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Sample records for rich nuclei close

  1. Pair correlations in neutron-rich nuclei

    SciTech Connect

    Esbensen, H.

    1995-08-01

    We started a program to study the ground-state properties of heavy, neutron-rich nuclei using the Hartree-Fock-Bogolyubov (HFB) approximation. This appears at present to be the most realistic approach for heavy nuclei that contain many loosely bound valence neutrons. The two-neutron density obtained in this approach can be decomposed into two components, one associated with the mean field and one associated with the pairing field. The latter has a structure that is quite similar to the pair-density obtained by diagonalizing the Hamiltonian for a two-neutron halo, which was studied earlier. This allows comparison of the HFB solutions against numerically exact solutions for two-neutron halos. This work is in progress. We intend to apply the HFB method to predict the ground-state properties of heavier, more neutron-rich nuclei that may be produced at future radioactive beam facilities.

  2. On Closed Shells in Nuclei

    DOE R&D Accomplishments Database

    Mayer, M. G.

    1948-02-01

    It has been suggested in the past that special numbers of neutrons or protons in the nucleus form a particularly stable configuration.{sup1} The complete evidence for this has never been summarized, nor is it generally recognized how convincing this evidence is. That 20 neutrons or protons (Ca{sup40}) form a closed shell is predicted by the Hartree model. A number of calculations support this fact.{sup2} These considerations will not be repeated here. In this paper, the experimental facts indicating a particular stability of shells of 50 and 82 protons and of 50, 82, and 126 neutrons will be listed.

  3. Formation of Heavy and Superheavy Neutron Rich Nuclei

    SciTech Connect

    Zagrebaev, Valery; Greiner, Walter

    2010-04-30

    A new way is proposed to discover and examine unknown neutron-rich heavy and superheavy nuclei at the 'north-east' part of the nuclear map. The present limits of the upper part of the nuclear map is very close to stability while the unexplored area of heavy neutron-rich nuclides to the east of the stability line (also those located along the neutron closed shell N = 126) is extremely important for nuclear astrophysics investigations and for the understanding of the r-process of astrophysical nucleo-genesis. A novel idea is proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions using a gain given by the shell effects. This finding may spur new studies at heavy ion facilities and should have significant impact for future experiments. The use of the multi-nucleon transfer reactions in low-energy collisions of heavy actinide nuclei gives us also the only chance to approach the 'island of stability' of superheavy elements. A possibility for a three-body decay (heavy ternary fission) is predicted for superheavy nuclei.

  4. Production of new neutron-rich heavy nuclei

    SciTech Connect

    Zagrebaev, Valery; Greiner, Walter

    2009-03-04

    A new way is found to discover and examine unknown neutron-rich heavy nuclei at the 'north-east' part of the nuclear map. This 'blank spot' of the nuclear map can be reached neither in fusion--fission reactions nor in fragmentation processes. The present limits of the upper part of the nuclear map are very close to stability while the unexplored area of heavy neutron-rich nuclides along the neutron closed shell N = 126(to the east of the stability line) is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. A novel idea is proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions with stable beams. The estimated yields of neutron-rich nuclei are found to be rather high in such reactions and several tens of new nuclides can be produced, for example, in the near-barrier collision of {sup 136}Xe with {sup 208}Pb. This finding may spur new studies at heavy-ion facilities and should have significant impact on future experiments.

  5. Clusters in neutron-rich light nuclei

    NASA Astrophysics Data System (ADS)

    Jelavić Malenica, D.; Milin, M.; Di Pietro, A.; Figuera, P.; Lattuada, M.; Miljanić, D.; Musumarra, A.; Pellegriti, M. G.; Prepolec, L.; Scuderi, V.; Skukan, N.; Soić, N.; Torresi, D.; Uroić, M.

    2016-05-01

    Due to their high selectivity, transfer and sequential decay reactions are powerful tools for studies of both single particle (nucleon) and cluster states in light nuclei. Their use is particularly simple for investigations of α-particle clustering (because α-particle has Jπ=0+, which simplifies spin and parity assignments to observed cluster states), but they are also easily applicable to other types of clustering. Recent results on clustering in neutron-rich isotopes of beryllium, boron and carbon obtained measuring the 10B+10B reactions (at 50 and 72 MeV) are presented. The highly efficient and segmented detector systems used, built from 4 Double Sided Silicon Strip Detectors (DSSSD) allowed detection of double and multiple coincidences and, in that way, studies of states populated in transfer reactions, as well as their sequential decay.

  6. Neutron transfer measurements on neutron-rich N=82 nuclei

    SciTech Connect

    Pain, Steven D; Jones, K. L.; Bardayan, Daniel W; Blackmon, Jeff C; Chae, K. Y.; Chipps, K.; Cizewski, J. A.; Hatarik, Robert; Kapler, R.; Kozub, R. L.; Liang, J Felix; Moazen, Brian; Nesaraja, Caroline D; Shapira, Dan; ShrinerJr., J. F.; Smith, Michael Scott

    2009-01-01

    Calculations of r-process nucleosynthesis rely significantly on nuclear structure models as input, which are not well tested in the neutron-rich regime, due to the paucity of experimental data on the majority of these nuclei. High quality radioactive beams have recently made possible the measurement of (d,p) reactions on unstable nuclei in inverse kinematics, which can yield information on the development of single-neutron structure away from stability in close proximity to suggested r-process paths. The Oak Ridge Rutgers University Barrel Array (ORRUBA) has been developed for the measurement of such reactions. An early partial implementation of ORRUBA has been utilized to measure the {sup 132}Sn(d,p){sup 133}Sn and {sup 134}Te(d,p){sup 135}Te reactions for the first time.

  7. Experimental study of neutron-rich nuclei near the N = 82 closed shell using the 4096Zr +50124Sn reaction with GASP and PRISMA-CLARA arrays

    NASA Astrophysics Data System (ADS)

    Rodríguez, W.; Torres, D. A.; Cristancho, F.; Medina, N. H.; Chapman, R.; Smith, J. F.; Mengoni, D.; Truesdale, V.; Grocutt, L.; Mulholland, K.; Kumar, V.; Hadinia, B.; Labiche, M.; Liang, X.; O'Donell, D.; Ollier, J.; Orlandi, R.; Smith, J. F.; Spohr, K. M.; Wady, P.; Wang, Z. M.; Gadea, A.; Ur, C. A.; Lenzi, S. M.; Capponi, L.; Michelangnoli, C.; Bazzacco, D.; Beghini, S.; Mǎrginean, R.; Mengoni, D.; Montagnoli, G.; Recchia, F.; Scarlassara, F.; Lunardi, S.; Kröll, T.; Napoli, D. R.; Corradi, L.; Fioretto, E.; de Angelis, G.; Mǎrginean, N.; Sahin, E.; Stefanini, A. M.; Valiente-Dobon, J. J.; Vedova, F. D.; Axiotis, M.; Martinez, T.; Szilner, S.; Freeman, S. J.; Smith, A. G.; Jones, G.; Thompson, N.; Pollarolo, G.

    2014-11-01

    In this contribution an experimental study of the deep-inelastic reaction 4096Zr +50124Sn at 530 MeV, using the GASP and PRISMA-CLARA arrays, is presented. The experiments populate a wealth of projectile-like and target-like binary fragments, in a large neutron-rich region around N ≥ 50 and Z ≈ 40. Preliminary results on the study of the yrast and near-yrast states for 95Nb will be shown, along with a comparison of the experimental yields obtained in the experiments.

  8. Relativistic mean field calculations in neutron-rich nuclei

    SciTech Connect

    Gangopadhyay, G.; Bhattacharya, Madhubrata; Roy, Subinit

    2014-08-14

    Relativistic mean field calculations have been employed to study neutron rich nuclei. The Lagrange's equations have been solved in the co-ordinate space. The effect of the continuum has been effectively taken into account through the method of resonant continuum. It is found that BCS approximation performs as well as a more involved Relativistic Continuum Hartree Bogoliubov approach. Calculations reveal the possibility of modification of magic numbers in neutron rich nuclei. Calculation for low energy proton scattering cross sections shows that the present approach reproduces the density in very light neutron rich nuclei.

  9. Modes of decay in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Kumar, B.; Biswal, S. K.; Singh, S. K.; Lahiri, C.; Patra, S. K.

    2016-03-01

    We calculate the ground, first intrinsic excited states and density distribution for neutron-rich thorium and uranium isotopes, within the framework of relativistic mean field (RMF) approach using axially deformed basis. The total nucleon densities are calculated, from which the cluster-structures inside the parent nuclei are determined. The possible modes of decay, like α-decay and β-decay are analyzed. We find the neutron-rich isotopes are stable against α-decay, however they are very much unstable against β-decay. The life time of these nuclei predicted to be tens of second against β-decay.

  10. New Neutron Rich Nuclei Near {sup 208}Pb

    SciTech Connect

    Aeystoe, J.; Andreyev, A.; Evensen, A.-H.; Hoff, P.; Huhta, M.; Huyse, M.; ISOLDE Collaboration; Jokinen, A.; Karny, M.; Kugler, E.; Kurpeta, J.; Lettry, J.; Nieminen, A.; Plochocki, A.; Ramdhane, M.; Ravn, H.; Rykaczewski, K.; Szerypo, J.; VanDuppen, P.; Walter, G.; Woehr, A.

    1998-11-13

    The level properties near the stable doubly-magic nuclei formed the experimental grounds for the theoretical description of nuclear structure. However with a departure from the beta-stability line, the classical well-established shell structure might be modified. In particular, it may even vanish for extremely exotic neutron-rich nuclei near the neutron-drip line. Presently, it is impossible to verify such predictions by a direct experimental studies of these exotic objects. However, one may try to observe and understand the evolution of the nuclear structure while departing in the experiment as far as possible from the stable nuclei. An extension of experimental nuclear structure studies towards the nuclei characterized by high neutron excess is crucial for such verifications as well as for the {tau}-process nucleosynthesis scenario. Heavy neutron-rich nuclei, south-east of doubly-magic {sup 208}Pb, were always very difficult to produce and investigate. The nuclei like {sup 218}Po and {sup 214}Pb or {sup 210}Tl marked the border line of known nuclei from the beginning of the radioactivity era for over ninety years. To illustrate the difficulties, one can refer to the experiments employing the on-line mass separator technique. A spallation of heavy targets like {sup 232}Th and {sup 238}U by high-energy protons was proven as a source of heavy neutron-rich nuclei. The isotopes near and beyond doubly-magic {sup 208}Pb were produced too. However, such studies often suffered from an isobaric contamination of much more strongly produced and efficiently released elements like francium or radon and their decay products. A new experimental technique, based on the pulsed release element selective method recently developed at the PS Booster-ISOLDE at CERN [7,8,9] greatly reduces the contamination of these very short-lived {alpha}-emitters (Z {ge} 84) for the isobaric mass chains A=215 to A=218.

  11. On Closed Shells in Nuclei. II

    DOE R&D Accomplishments Database

    Mayer, M. G.

    1949-04-01

    Discussion on the use of spins and magnetic moments of the even-odd nuclei by Feenberg and Nordheim to determine the angular momentum of the eigenfunction of the odd particle; discussion of prevalence of isomerism in certain regions of the isotope chart; tabulated data on levels of square well potential, spectroscopic levels, spin term, number of states, shells and known spins and orbital assignments.

  12. Beta decay rates of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Marketin, Tomislav; Huther, Lutz; Petković, Jelena; Paar, Nils; Martínez-Pinedo, Gabriel

    2016-06-01

    Heavy element nucleosynthesis models involve various properties of thousands of nuclei in order to simulate the intricate details of the process. By necessity, as most of these nuclei cannot be studied in a controlled environment, these models must rely on the nuclear structure models for input. Of all the properties, the beta-decay half-lives are one of the most important ones due to their direct impact on the resulting abundance distributions. In this study we present the results of a large-scale calculation based on the relativistic nuclear energy density functional, where both the allowed and the first-forbidden transitions are studied in more than 5000 neutron-rich nuclei. Aside from the astrophysical applications, the results of this calculation can also be employed in the modeling of the electron and antineutrino spectra from nuclear reactors.

  13. The pygmy dipole resonance in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Quang Hung, Nguyen; Kiet, Hoang Anh Tuan; Duc, Huynh Ngoc; Thi Chuong, Nguyen

    2016-06-01

    The pygmy dipole resonance (PDR), which has been observed via the enhancement of the electric dipole strength E1 of atomic nuclei, is studied within a microscopic collective model. The latter employs the Hartree-Fock (HF) method with effective nucleon-nucleon interactions of the Skyrme types plus the random-phase approximation (RPA). The results of the calculations obtained for various even-even nuclei such as 16-28O, 40-58Ca, 100-120Sn, and 182-218Pb show that the PDR is significantly enhanced when the number of neutrons outside the stable core of the nucleus is increased, that is, in the neutron-rich nuclei. As the result, the relative ratio between the energy weighted sum of the strength of the PDR and that of the GDR (giant dipole resonance) does not exceed 4%. The collectivity of the PDR and GDR states will be also discussed.

  14. Beta decay rates of neutron-rich nuclei

    SciTech Connect

    Marketin, Tomislav; Huther, Lutz; Martínez-Pinedo, Gabriel

    2015-10-15

    Heavy element nucleosynthesis models involve various properties of thousands of nuclei in order to simulate the intricate details of the process. By necessity, as most of these nuclei cannot be studied in a controlled environment, these models must rely on the nuclear structure models for input. Of all the properties, the beta-decay half-lives are one of the most important ones due to their direct impact on the resulting abundance distributions. Currently, a single large-scale calculation is available based on a QRPA calculation with a schematic interaction on top of the Finite Range Droplet Model. In this study we present the results of a large-scale calculation based on the relativistic nuclear energy density functional, where both the allowed and the first-forbidden transitions are studied in more than 5000 neutron-rich nuclei.

  15. Evidence for dineutrons in extremely neutron-rich nuclei

    SciTech Connect

    Seth, K.K.; Parker, B. )

    1991-05-13

    It is shown that the continuum missing-mass spectra for the ({pi}{sup {minus}},{pi}{sup +}) and ({pi}{sup {minus}},{ital p}) reactions leading to extremely neutron-rich exotic nuclei can be explained in terms of phase-space distributions by invoking the presence of dineutrons as one of the products of the breakup. It is suggested that this indicates the presence of the dineutron as a cluster in these neutron-rich systems during their breakup. It is noted that these observations in weakly {ital unbound} systems may be analogs of the dineutron halos for which evidence has been found in weakly {ital bound} nuclei near the neutron drip line.

  16. Spectroscopic studies on light proton-rich nuclei

    SciTech Connect

    Guimaraes, V.; Lichtenthaler, R.; Kubono, S.; Tanaka, M. H.; Nomura, T.; Katayama, I.; Kato, S.

    2007-02-12

    A systematic for the light proton rich nuclei with constant TZ = -3/2 isospin is proposed, where a survey on their structure have shown interesting features. Preliminary results of a re-analysis on the sctructure of 13O nucleus is also presented. This 13O nucleus have been investigated by the 3-neutron pick up (3He,6He) reaction, and new levels have been assigned for this nucleus.

  17. Three-Body Forces and Proton-Rich Nuclei

    SciTech Connect

    Holt, Jason D; Menendez, J.

    2013-01-01

    We present the first study of three-nucleon (3N) forces for proton-rich nuclei along the N 8 and N 20 isotones. Our results for the ground-state energies and proton separation energies are in very good agreement with experiment where available, and with the empirical isobaric multiplet mass equation. We predict the spectra for all N 8 and N 20 isotones to the proton dripline, which agree well with experiment for 18Ne, 19Na, 20Mg and 42Ti. In all other cases, we provide first predictions based on nuclear forces. Our results are also very promising for studying isospin symmetry breaking in medium-mass nuclei based on chiral effective field theory.

  18. Quadrupole collectivity of neutron-rich nuclei around 132Sn

    NASA Astrophysics Data System (ADS)

    Kröll, Th.; Behrens, T.; Krücken, R.; Bildstein, V.; Faestermann, T.; Gernhäuser, R.; Mahgoub, M.; Maierbeck, P.; Münch, M.; Weinzierl, W.; Ames, F.; Habs, D.; Kester, O.; Lutter, R.; Morgan, T.; Pasini, M.; Rudolph, K.; Thirolf, P.; Diriken, J.; Huyse, M.; Ivanov, O.; Mayet, P.; Patronis, N.; Stefanescu, I.; van de Walle, J.; van Duppen, P.; Niedermaier, O.; Scheit, H.; Schwalm, D.; Eberth, J.; Finke, F.; Martin, D.; Reiter, P.; Scherillo, A.; Seidlitz, M.; Warr, N.; Weisshaar, D.; Iwanicki, J.; Butler, P.; Cederkäll, J.; Clément, E.; Delahaye, P.; Fraile, L. M.; Georgiev, G.; Köster, U.; Sieber, T.; Voulot, D.; Wenander, F.; Franchoo, S.; Hurst, A.; Ekström, A.; Kent, P. E.; Speidel, K.-H.; Leske, J.; Schielke, S.; Jungclaus, A.; Modamio, V.; Walker, J.; Coquard, L.; Pantea, M.; Pietralla, N.; Davinson, T.; Nardelli, S.

    2008-05-01

    We report on the ``safe'' Coulomb excitation of neutron-rich Cd, Xe, and Ba isotopes in the vicinity of the doubly-magic nucleus 132Sn. The radioactive nuclei have been produced by ISOLDE at CERN and postaccelerated by the REX-ISOLDE facility. The γ-decay of excited states has been detected by the MINIBALL array. The presented preliminary results for the B(E2) values are consistent with expectations from phenomenological systematics and will be compared with theoretical calculations.

  19. Fission and Properties of Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Hamilton, Joseph H.; Ramayya, A. V.; Carter, H. K.

    2008-08-01

    Opening session. Nuclear processes in stellar explosions / M. Wiescher. In-beam [symbol]-ray spectroscopy of neutron-rich nuclei at NSCL / A. Gade -- Nuclear structure I. Shell-model structure of neutron-rich nuclei beyond [symbol]Sn / A. Covello ... [et al.]. Shell structure and evolution of collectivity in nuclei above the [symbol]Sn core / S. Sarkar and M. S. Sarkar. Heavy-ion fusion using density-constrained TDHF / A. S. Umar and V. E. Oberacker. Towards an extended microscopic theory for upper-fp shell nuclei / K. P. Drumev. Properties of the Zr and Pb isotopes near the drip-line / V. N. Tarasov ... [et al.]. Identification of high spin states in [symbol] Cs nuclei and shell model calculations / K. Li ... [et al.]. Recent measurements of spherical and deformed isomers using the Lohengrin fission-fragment spectrometer / G. S. Simpson ... [et al.] -- Nuclear structure II. Nuclear structure investigation with rare isotope spectroscopic investigations at GSI / P. Boutachkov. Exploring the evolution of the shell structures by means of deep inelastic reactions / G. de Anaelis. Probing shell closures in neutron-rich nuclei / R. Krücken for the S277 and REX-ISOLDEMINIBALL collaborations. Structure of Fe isotopes at the limits of the pf-shell / N. Hoteling ... [et al.]. Spectroscopy of K isomers in shell-stabilized trans-fermium nuclei / S. K. Tandel ... [et al.] -- Radioactive ion beam facilities. SPIRAL2 at GANIL: a world leading ISOL facility for the next decade / S. Gales. New physics at the International Facility for Antiproton and Ion Research (FAIR) next to GSI / I. Augustin ... [et al.]. Radioactive beams from a high powered ISOL system / A. C. Shotter. RlKEN RT beam factory / T. Motobayashi. NSCL - ongoing activities and future perspectives / C. K. Gelbke. Rare isotope beams at Argonne / W. F. Henning. HRIBF: scientific highlights and future prospects / J. R. Beene. Radioactive ion beam research done in Dubna / G. M. Ter-Akopian ... [et al.] -- Fission I

  20. Probing Shell Closures in Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Krücken, R.

    2008-08-01

    Results of two experimental campaigns are presented investigating shell structure in neutron-rich nuclei near 54Ca and 132Sn, respectively. In the first experiment excited states in 55Ti were investigated at the middle focus of the GSI FRS via one-neutron knock-out from 56Ti. Longitudinal momentum distributions were measured inclusively and in coincidence with a newly discovered gamma-ray at 955 keV detected by the MINIBALL gamma-ray detector array. From the momentum distributions the νp1/2 single-particle structure of the ground state was determined for the first time while the excited state at 955 keV is identified as the νp3/2 single-particle state. Secondly, results from the Coulomb excitation of neutron-rich nuclei 122,124,126Cd, 138,140,142,144Xe are presented. These experiments were performed at the REX-ISOLDE accelerator at CERN also using the MINIBALL array. The obtained B(E2)-values follow the expected systematic behavior that correlates the energy of the first excited 2+ state with the B(E2)-values and also agree well with the results of theoretical predictions.

  1. New prospects in synthesis and study of neutron rich heavy nuclei

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Mishustin, I. N.; Greiner, W.

    2011-10-01

    The present limits of the upper part of the nuclear map are rather close to the beta stability line while the unexplored area of heavy neutron rich nuclides (also those located along the neutron closed shell N = 126 to the right hand side of the stability line) is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. For elements with Z > 100 only neutron deficient isotopes (located to the left of the stability line) have been synthesized so far. The "north-east" area of the nuclear map can be reached neither in fusion-fission reactions nor in fragmentation processes widely used nowadays for the production of new nuclei. Multi-nucleon transfer processes in near barrier collisions of heavy ions seem to be the only reaction mechanism allowing us to produce and explore neutron rich heavy nuclei including those located at the superheavy island of stability. Neutron capture process can be also considered as an alternative method for the production of long-lived neutron rich superheavy nuclei. Strong neutron fluxes might be provided by nuclear reactors and nuclear explosions in laboratory frame and by supernova explosions in nature.

  2. New Band Structures in Aapprox110 Neutron-Rich Nuclei

    SciTech Connect

    Zhu, S. J.; Wang, J. G.; Ding, H. B.; Gu, L.; Xu, Q.; Yeoh, E. Y.; Xiao, Z. G.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Liu, S. H.; Li, K.; Luo, Y. X.; Rasmussen, J. O.; Lee, I. Y.; Qi, B.; Meng, J.

    2010-05-12

    The high spin states of neutron-rich nuclei in Aapprox110 region have been carefully investigated by measuring prompt gamma-gamma-gamma coincident measurements populated in the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. Many new collective bands have been discovered. In this proceeding paper, we introduce some interesting new band structures recently observed by our cooperative groups, that is, the one-phonon- and two-phonon gamma-vibrational bands in odd-A {sup 103}Nb, {sup 105}Mo and {sup 107}Tc, the chiral doublet bands in even-even {sup 106}Mo, {sup 110}Ru and {sup 112}Ru, and the pseudospin partner bands with in {sup 108}Tc. The characteristics of these band structures have been discussed.

  3. Shell structure in neutron rich nuclei by means of binary reactions

    SciTech Connect

    Angelis, G. de

    2014-08-14

    Nuclear structure studies far from stability rely mainly on the availability of radioactive nuclear beams but can complementary be addressed by means of high intensity beams of stable ions. In such contest, deep-inelastic and multinucleon transfer reactions are a powerful tool to populate yrast and non yrast states in neutron-rich nuclei. Particularly successful is here the combination of large acceptance spectrometers with highly segmented gamma-detector arrays. Such devices can provide the necessary channel selectivity to identify very rare signals. The AGATA gamma-ray detector array coupled to the PRISMA spectrometer at the Legnaro National Laboratories (LNL) in Italy is one example. Large data sets have been collected at LNL for nuclei close to the N=20, 28, 40, 50 and 82 shell closures.

  4. Radiative neutron captures by neutron-rich nuclei and the r-process nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Goriely, S.

    1998-09-01

    The radiative neutron capture by neutron-rich nuclei is estimated with an improved description of the electric giant dipole resonance. In addition, 3 major effects affecting the capture rates by exotic neutron-rich nuclei are studied. These concern the existence of a low-energy E1 pygmy resonance, the overestimate of the statistical predictions for resonance-deficient nuclei and the direct capture mechanism. The total (n,γ) reaction rates including these 3 effects are evaluated for 3100 neutron-rich nuclei and used in parametric r-process calculations to analyze their impact on the r-abundance distribution.

  5. Exotic modes of excitation in deformed neutron-rich nuclei

    SciTech Connect

    Yoshida, Kenichi

    2011-05-06

    Low-lying dipole excitation mode in neutron-rich Mg isotopes close to the drip line is investigated in the framework of the Hartree-Fock-Bogoliubov and the quasiparticle random-phase approximation employing the Skyrme and the pairing energy-density functionals. It is found that the low-lying dipole-strength distribution splits into the K{sup {pi}} = 0{sup -} and 1{sup -} components due to the nuclear deformation. The low-lying dipole strength increases as the neutron drip-line is approached.

  6. Technology-Rich Schools Up Close

    ERIC Educational Resources Information Center

    Levin, Barbara B.; Schrum, Lynne

    2013-01-01

    This article observes that schools that use technology well have key commonalities, including a project-based curriculum and supportive, distributed leadership. The authors' research into tech-rich schools revealed that schools used three strategies to integrate technology successfully. They did so by establishing the vision and culture,…

  7. Experimental study of neutron-rich nuclei near the N = 82 closed shell using the {sub 40}{sup 96}Zr+{sub 50}{sup 124}Sn reaction with GASP and PRISMA-CLARA arrays

    SciTech Connect

    Rodríguez, W.; Torres, D. A.; Cristancho, F.; Medina, N. H.; Chapman, R.; Smith, J. F.; Mengoni, D.; Truesdale, V.; Grocutt, L.; Mulholland, K.; Kumar, V.; Hadinia, B.; Labiche, M.; Liang, X.; O'Donell, D.; Ollier, J.; Orlandi, R.; Smith, J. F.; Spohr, K. M.; Wady, P.; and others

    2014-11-11

    In this contribution an experimental study of the deep-inelastic reaction {sub 40}{sup 96}Zr+{sub 50}{sup 124}Sn at 530 MeV, using the GASP and PRISMA-CLARA arrays, is presented. The experiments populate a wealth of projectile-like and target-like binary fragments, in a large neutron-rich region around N ≥ 50 and Z ≈ 40. Preliminary results on the study of the yrast and near-yrast states for {sup 95}Nb will be shown, along with a comparison of the experimental yields obtained in the experiments.

  8. Continuum Response and Reaction in Neutron-Rich Be Nuclei

    SciTech Connect

    Nakatsukasa, Takashi; Ueda, Manabu; Yabana, Kazuhiro

    2004-02-27

    We study E1 resonances, breakup and fusion reactions for weakly bound Be nuclei. The absorbing-boundary condition (ABC) is used to describe both the outgoing and incoming boundary conditions. The neutron continuum plays important roles in response and reaction of neutron drip-line nuclei.

  9. Spectroscopy of neutron-rich nuclei at REX-ISOLDE with MINIBALL

    NASA Astrophysics Data System (ADS)

    Kröll, Th.

    2007-08-01

    We report on “safe” Coulomb excitation of neutron-rich nuclei. The radioactive nuclei have been produced by ISOLDE at CERN and postaccelerated by the REX-ISOLDE facility. The γ rays emitted by the decay of excited states have been detected by the MINIBALL array. Recent results are presented and compared to theoretical models.

  10. Spectroscopy of neutron-rich nuclei at REX-ISOLDE with MINIBALL

    SciTech Connect

    Kroell, Th.

    2007-08-15

    We report on 'safe' Coulomb excitation of neutron-rich nuclei. The radioactive nuclei have been produced by ISOLDE at CERN and postaccelerated by the REX-ISOLDE facility. The {gamma} rays emitted by the decay of excited states have been detected by the MINIBALL array. Recent results are presented and compared to theoretical models.

  11. The Spectroscopy of Neutron-Rich sdf-Shell Nuclei Using the CLARA-PRISMA Setup

    SciTech Connect

    Liang, X.; Hodsdon, A.; Chapman, R.; Burns, M.; Keyes, K.; Ollier, J.; Papenberg, A.; Spohr, K.; Azaiez, F.; Ibrahim, F.; Stanoiu, M.; Haas, F.; Caurier, E.; Curien, D.; Nowacki, F.; Salsac, M.-D.; Bazzacco, D.; Beghini, S.; Farnea, E.; Menegazzo, R.

    2006-08-14

    Since the discovery of the breakdown of shell effects in very neutron-rich N=20 and 28 nuclei, studies of the properties of nuclei far from stability have been of intense interest since they provide a unique opportunity to increase our understanding of nuclear interactions in extreme conditions and often challenge our theoretical models.Deep-inelastic processes can be used to populated high spin states of neutron-rich nuclei. In the deep-inelastic processes, an equilibration in N/Z between the target and projectile nuclei is achieved. For most heavy neutron-rich target nuclei, the N/Z ratio is 1.5 - 1.6, while for the possible neutron-rich sdf-shell projectile it is about 1.2. Thus by using deep-inelastic processes one can populate neutron-rich nuclei around N=20 and N=28.New results for the spectroscopy of neutron-rich N=22 36Si and 37P are presented here.

  12. Shell And Halo Structure In Neutron-Rich Light Nuclei

    SciTech Connect

    Nociforo, C.

    2010-06-01

    Spectroscopic investigations performed at the neutron drip line in case of sd shell nuclei have recently shown the existence of the new magic numbers Z = 8 and N = 14,16. Predictions within the nuclear shell model calculations for the {sup 23,24}O ground state have been confirmed measuring their neutron occupancy in breakup reactions performed by using the inflight radioactive ion beams produced at the Fragment Separator FRS of GSI. Some perspectives of studying the evolution of magic numbers in this region of light exotic nuclei are given.

  13. Static and dynamic aspect of covariant density functional theory in proton rich nuclei

    SciTech Connect

    Ring, P.; Lalazissis, G. A.; Paar, N.; Vretenar, D.

    2007-11-30

    Proton rich nuclei are investigated in the framework of Covariant Density Functional Theory (CDFT). The Relativistic Hartree Bogoliubov (RHB) model is used to study the proton drip line in the region of heavy and superheavy nuclei. The dynamical behavior of nuclei with a large proton excess is studied within the Relativistic Quasiparticle Random Phase Approximation (RQRPA). Low lying El-strength is observed and it is shown that it corresponds to an oscillation of the proton skin against the isospin saturated neutron-proton core. This mode is in full analogy to the neutron pygmy resonances found in many nuclei with neutron excess.

  14. Interplay between collective and single particle excitations around neutron-rich doubly-magic nuclei

    NASA Astrophysics Data System (ADS)

    Leoni, S.

    2016-05-01

    The excitation spectra of nuclei with one or two particles outside a doubly-magic core are expected to be dominated, at low energy, by the couplings between phonon excitations of the core and valence particles. A survey of the experimental situation is given for some nuclei lying in close proximity of neutron-rich doubly-magic systems, such as 47,49Ca, 133Sb and 210Bi. Data are obtained with various types of reactions (multinucleon transfer with heavy ions, cold neutron capture and neutron induced fission of 235U and 241Pu targets), with the employment of complex detection systems based on HPGe arrays. A comparison with theoretical calculations is also presented, in terms of large shell model calculations and of a phenomenological particle-phonon model. In the case of 133Sb, a new microscopic "hybrid" model is introduced: it is based on the coupling between core excitations (both collective and non-collective) of the doubly-magic core and the valence nucleon, using the Skyrme effective interaction in a consistent way.

  15. Spectroscopy of Neutron-rich Nuclei of the A{approx_equal}60 region populated through binary heavy-ion collisions

    SciTech Connect

    Lunardi, S.

    2008-11-11

    Neutron-rich nuclei of the mass A = 60 region (from V to Fe) have been studied through multi-nucleon transfer reactions by bombarding a {sup 238}U target with beams of {sup 64}Ni and {sup 70}Zn. Unambiguous identification of prompt {gamma} rays belonging to each nucleus has been achieved by using the efficient gamma-array CLARA coupled to the large-acceptance magnetic spectrometer PRISMA installed at the Legnaro National Laboratories. With the new data, the existence of the N = 32 sub-shell closure has been corroborated through the study of odd V isotopes, whereas a new region of deformation appears for neutron-rich Fe nuclei close to N = 40. The results obtained for all these nuclei are compared with shell model calculations which reproduces quite well the experimental data also for the most neutron-rich nuclei when excitations from the fp shell into the upper g{sub 9/2} orbital are allowed.

  16. Structure of Light Neutron-rich Nuclei Studied with Transfer Reactions

    SciTech Connect

    Wuosmaa, A. H.

    2015-01-01

    Transfer reactions have been used for many years to understand the shell structure of nuclei. Recent studies with rare-isotope beams extend this work and make it possible to probe the evolution of shell structure far beyond the valley of stability, requiring measurements in inverse kinematics. We present a novel technical approach to measurements in inverse kinematics, and apply this method to different transfer reactions, each of which probes different properties of light, neutron-rich nuclei.

  17. One-neutron knockout from light neutron-rich nuclei at relativistic energies

    SciTech Connect

    Rodriguez-Tajes, C.; Alvarez-Pol, H.; Benjamim, E.; Benlliure, J.; Caamano, M.; Casarejos, E.; Cortina-Gil, D.; Gascon, M.; Kurtukian, T.; Perez-Loureiro, D.; Aumann, T.; Chatillon, A.; Geissel, H.; Nociforo, C.; Prochazka, A.; Simon, H.; Suemmerer, K.; Weick, H.; Winkler, M.; Borge, M. J. G.

    2010-08-15

    One-neutron knockout reactions from neutron-rich nuclei, with Z=6-13 and N=8-22, were studied at the Fragment Separator (GSI) at high beam energies, around 700 MeV/nucleon. Structural phenomena such as the formation of one-neutron halos in odd-mass carbon isotopes ({sup 15,17,19}C) will be discussed. In addition, one-neutron knockout measurements from {sup 22}N were carried out for the first time and demonstrate clearly the change from a 0d{sub 5/2} to a 1s{sub 1/2} orbital for the valence neutron, an effect that is expected above N=14 and that was also observed in {sup 23}O and {sup 24}F. The possibility of an anomalous structure of {sup 26}F, due to a significant 1s{sub 1/2} neutron admixture, will also be discussed in the light of the experimental data obtained in this work. Finally, the ground-state configuration of neutron-rich neon isotopes ({sup 24-28}Ne) was studied, providing new information in a region that is relatively close to the island of inversion.

  18. Nucleosynthesis of neutron-rich heavy nuclei during explosive helium burning in massive stars

    NASA Technical Reports Server (NTRS)

    Blake, J. B.; Woosley, S. E.; Weaver, T. A.; Schramm, D. N.

    1981-01-01

    The production of heavy nuclei during explosive helium burning has been calculated using a hydrodynamical model of a 15-solar mass (Type II) supernova and an n-process nuclear reaction network. It is found that the resulting neutron-rich heavy nuclei are not produced in the relative abundances of solar-system r-process material, especially in the vicinity of Pt, nor are any actinides produced. These deficiencies reflect an inadequate supply of neutrons. However, some neutron-rich isotopes, normally associated with the r-process, are produced which may be significant for the production of isotopic anomalies in meteorites.

  19. Predicted yields of new neutron-rich isotopes of nuclei with Z=64-80 in the multinucleon transfer reaction {sup 48}Ca+{sup 238}U

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.; Scheid, W.

    2010-05-15

    The production cross sections of new neutron-rich isotopes of nuclei with charge numbers Z=64-80 are estimated for future experiments in the multinucleon transfer reaction {sup 48}Ca+{sup 238}U at bombarding energy E{sub c.m.}=189 MeV close to the Coulomb barrier.

  20. Upbend and M1 scissors mode in neutron-rich nuclei - consequences for r-process $$(n,\\gamma )$$ reaction rates

    DOE PAGES

    Larsen, A. C.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Bracco, A.; Brown, B. A.; Camera, F.; Eriksen, T. K.; Frauendorf, S.; Giacoppo, F.; et al

    2015-01-01

    An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. Furthermore, the experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

  1. Upbend and M1 scissors mode in neutron-rich nuclei - consequences for r-process $(n,\\gamma )$ reaction rates

    SciTech Connect

    Larsen, A. C.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Bracco, A.; Brown, B. A.; Camera, F.; Eriksen, T. K.; Frauendorf, S.; Giacoppo, F.; Guttormsen, M.; Gorgen, A.; Harissopulos, S.; Leoni, S.; Liddick, S. N.; Naqvi, F.; Nyhus, H. T.; Rose, S. J.; Renstrom, T.; Schwengner, R.; Siem, S.; Spyrou, A.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.

    2015-01-01

    An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. Furthermore, the experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

  2. Production and identification of new, neutron-rich nuclei in the [sup 208]Pb region

    SciTech Connect

    Rykaczewski, K. ); Szerypo, J.; Evensen, A.-H.; Kugler, E.; Lettry, J.; Ravn, H. ); Kurpeta, J.; Pkochocki, A.; Karny, M.; Szerypo, J. ); Szerypo, J. ); Andreyev, H.; Huyse, M.; Wo uml; hr, A. ); Aystuml, J.; Nieminen, A.; Huhta, M. ); Walter, G. ) Hoff, P. )

    1998-12-01

    The recently developed methods allowing the experimental studies on new neutron-rich nuclei beyond doubly-magic [sup 208]Pb are briefly described. An identification of new neutron-rich isotopes [sup 215]Pb and [sup 217]Bi, and new decay properties of [sup 216]Bi studied by means of a pulsed release element selective technique at PS Booster-ISOLDE are reported. [copyright] [ital 1998 American Institute of Physics.

  3. Studies of neutron-rich nuclei using the CPT mass spectrometer at CARIBU

    NASA Astrophysics Data System (ADS)

    Chaudhuri, A.; Bertone, P. F.; Buchinger, F.; Caldwell, S.; Clark, J. A.; Crawford, J. E.; Deibel, C. M.; Gulick, S.; Lascar, D.; Levand, A. F.; Li, G.; Savard, G.; Segel, R. E.; Sharma, K. S.; Sternberg, M. G.; Sun, T.; Van Schelt, J.

    2011-09-01

    The nucleosynthetic path of the astrophysical r-process and the resulting elemental abundances depend on neutron-separation energies which can be determined from the masses of the nuclei along the r-process reaction path. Due to the current lack of experimental data, mass models are often used. The mass values provided by the mass models are often too imprecise or disagree with each other. Therefore, direct high-precision mass measurements of neutron-rich nuclei are necessary to provide input parameters to the calculations and help refine the mass models. The Californium Rare Isotope Breeder Upgrade (CARIBU) facility of Argonne National Laboratory will provide experiments with beams of short-lived neutron-rich nuclei. The Canadian Penning Trap (CPT) mass spectrometer has been relocated to the CARIBU low-energy beam line to extend measurements of the neutron-rich nuclei into the mostly unexplored region along the r-process path. This will allow precise mass measurements (~ 10 keV/c2) of more than a hundred very neutron-rich isotopes that have not previously been measured.

  4. Production of heavy and superheavy neutron-rich nuclei in neutron capture processes

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Mishustin, I. N.; Greiner, Walter

    2011-10-01

    The neutron capture process is considered as an alternative method for production of superheavy (SH) nuclei. Strong neutron fluxes might be provided by nuclear reactors and nuclear explosions in the laboratory frame and by supernova explosions in nature. All these cases are discussed in the paper. There are two gaps of short-lived nuclei (one is the well-known fermium gap and the other one is located in the region of Z=106-108 and N˜170) which impede the formation of SH nuclei by rather weak neutron fluxes realized at available nuclear reactors. We find that in the course of multiple (rather “soft”) nuclear explosions these gaps may be easily bypassed, and thus, a measurable amount of the neutron-rich long-living SH nuclei located at the island of stability may be synthesized. Existing pulsed reactors do not allow one to bypass these gaps. We formulate requirements for the pulsed reactors of the next generation that could be used for production of long-living SH nuclei. Natural formation of SH nuclei (in supernova explosions) is also discussed. The yield of SH nuclei relative to lead is estimated to be about 10-12, which is not beyond the experimental sensitivity for a search of SH elements in cosmic rays.

  5. Collective Band Structures in the Neutron-Rich 107,109Ru Nuclei

    NASA Astrophysics Data System (ADS)

    Zhu, Sheng-jiang; Gan, Cui-yun; J, Hamilton H.; A, Ramayya V.; B, Babu R. S.; M, Sakhaee; W, Ma C.; Long, Gui-lu; Deng, Jing-kang; Zhu, Ling-yan; Li, Ming; Yang, Li-ming; J, Komicki; J, Cole D.; R, Aryaeinejad; Y, Dardenne K.; M, Drigert W.; J, Rasmussen O.; M, Stoyer A.; S, Chu Y.; K, Gregorich E.; M, Mohar F.; S, Prussin G.; I, Lee Y.; N, Johnson R.; F, McGowan K.

    1998-11-01

    The levels in neutron-rich odd-A 107,109Ru nuclei have been investigated by using γ-γ- and γ-γ-γ-coincidence studies of the prompt γ-rays from the spontaneous fission of 252Cf. The ground state bands and the negative parity bands are identified and expanded in both nuclei. Triaxial rotor plus particle model calculations indicate the ground state bands originate from ν(d5/2 + g7/2) quasiparticle configurations and the negative parity bands are from νh11/2 orbital.

  6. Shell-model study for neutron-rich sd-shell nuclei

    SciTech Connect

    Kaneko, Kazunari; Sun Yang; Mizusaki, Takahiro; Hasegawa, Munetake

    2011-01-15

    The microscopic structure of neutron-rich sd-shell nuclei is investigated by using the spherical-shell model in the sd-pf valence space with the extended pairing plus quadrupole-quadrupole forces accompanied by the monopole interaction (EPQQM). The calculation reproduces systematically the known energy levels for even-even and odd-mass nuclei including the recent data for {sup 43}S, {sup 46}S, and {sup 47}Ar. In particular, the erosion of the N=28 shell closure in {sup 42}Si can be explained. Our EPQQM results are compared with other shell-model calculations with the SDPF-NR and SDPF-U effective interactions.

  7. Two-Neutron Separation Energies Of Even-Even Rare-Earth Neutron-Rich Nuclei

    SciTech Connect

    Benhamouda, N.; Oudih, M. R.; Allal, N. H.; Fellah, M.

    2007-04-23

    The variation of the two-neutron separation energy (S2N), as a function of N, is studied using a microscopic model that includes the pairing effects rigorously within the Fixed-Sharp-BCS method. The model has been tested for ''ordinary'' nuclei and has correctly reproduced the experimental data. The study has then been extended to the neutron-rich nuclei and has shown a relatively important variation of S2N when N= 100 which may be attributed to the existence of a new magic number.

  8. Studies of neutron-rich nuclei far from stability at TRISTAN

    SciTech Connect

    Gill, R.L.

    1984-01-01

    The ISOL facility, TRISTAN, is a user facility located at Brookhaven National Laboratory's High Flux Beam Reactor. Short-lived, neutron-rich nuclei, far from stability, are produced by thermal neutron fission of /sup 235/U. An extensive array of experimental end stations are available for nuclear structure studies. These studies are augmented by a variety of long-lived ion sources suitable for use at a reactor facility. Some recent results at TRISTAN are presented as examples of using an ISOL facility to study series of nuclei, whereby an effective means of conducting nuclear structure investigations is available.

  9. Magicity of neutron-rich nuclei within relativistic self-consistent approaches

    NASA Astrophysics Data System (ADS)

    Li, Jia Jie; Margueron, Jérôme; Long, Wen Hui; Van Giai, Nguyen

    2016-02-01

    The formation of new shell gaps in intermediate mass neutron-rich nuclei is investigated within the relativistic Hartree-Fock-Bogoliubov theory, and the role of the Lorentz pseudo-vector and tensor interactions is analyzed. Based on the Foldy-Wouthuysen transformation, we discuss in detail the role played by the different terms of the Lorentz pseudo-vector and tensor interactions in the appearing of the N = 16, 32 and 34 shell gaps. The nuclei 24O, 48Si and 52,54Ca are predicted with a large shell gap and zero (24O, 52Ca) or almost zero (48Si, 54Ca) pairing gap, making them candidates for new magic numbers in exotic nuclei. We find from our analysis that the Lorentz pseudo-vector and tensor interactions induce very specific evolutions of single-particle energies, which could clearly sign their presence and reveal the need for relativistic approaches with exchange interactions.

  10. Cluster-transfer reactions with radioactive beams: A spectroscopic tool for neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Bottoni, S.; Leoni, S.; Fornal, B.; Raabe, R.; Rusek, K.; Benzoni, G.; Bracco, A.; Crespi, F. C. L.; Morales, A. I.; Bednarczyk, P.; Cieplicka-Oryńczak, N.; Królas, W.; Maj, A.; Szpak, B.; Callens, M.; Bouma, J.; Elseviers, J.; De Witte, H.; Flavigny, F.; Orlandi, R.; Reiter, P.; Seidlitz, M.; Warr, N.; Siebeck, B.; Hellgartner, S.; Mücher, D.; Pakarinen, J.; Vermeulen, M.; Bauer, C.; Georgiev, G.; Janssens, R. V. F.; Balabanski, D.; Sferrazza, M.; Kowalska, M.; Rapisarda, E.; Voulot, D.; Lozano Benito, M.; Wenander, F.

    2015-08-01

    An exploratory experiment performed at REX-ISOLDE to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier as a mechanism to explore the structure of exotic neutron-rich nuclei. The reactions 7Li(98Rb,α xn ) and 7Li(98Rb,t xn ) were studied through particle-γ coincidence measurements, and the results are presented in terms of the observed excitation energies and spins. Moreover, the reaction mechanism is qualitatively discussed as a transfer of a clusterlike particle within a distorted-wave Born approximation framework. The results indicate that cluster-transfer reactions can be described well as a direct process and that they can be an efficient method to investigate the structure of neutron-rich nuclei at medium-high excitation energies and spins.

  11. Evolution of collective structures in the heavy transitional nuclei above the N = 82 closed shell

    NASA Astrophysics Data System (ADS)

    Joss, D. T.

    2016-09-01

    The emergence of collectivity in atomic nuclei is a fundamental paradigm in nuclear structure physics. Considerable progress has been made towards the identification of excited states in heavy neutrondeficient nuclei above the N = 82 closed shell. This paper summarises recent progress in the spectroscopic study of the Ta, W and Re nuclides with N ˜ 90 obtained from recoil and recoil-decay tagging experiments. The nuclei near N = 90 occupy γ-soft transitional region where the nuclear shape is particularly sensitive to the interplay between collective excitations and the underlying single-particle structure. The consequences of these interactions for low and high-spin states are discussed.

  12. Dipole response in neutron-rich nuclei with new Skyrme interactions

    NASA Astrophysics Data System (ADS)

    Zheng, H.; Burrello, S.; Colonna, M.; Baran, V.

    2016-07-01

    We investigate the isoscalar and isovector E 1 response of neutron-rich nuclei, within a semiclassical transport model employing effective interactions for the nuclear mean field. In particular, we adopt the recently introduced SAMi-J Skyrme interactions, whose parameters are specifically tuned to improve the description of spin-isospin properties of nuclei. Our analysis evidences a relevant degree of isoscalar-isovector mixing of the collective excitations developing in neutron-rich systems. Focusing on the low-lying strength emerging in the isovector response, we show that this energy region essentially corresponds to the excitation of isoscalar-like modes, which also contribute to the isovector response owing to their mixed character. Considering effective interactions which mostly differ in the isovector channels, we observe that these mixing effects increase with the slope L of the symmetry energy at saturation density, leading to a larger strength in the low-energy region of the isovector response. This result appears connected to the increase, with L , of the neutron-proton asymmetry at the surface of the considered nuclei, i.e., to the neutron skin thickness.

  13. Proton-Neutron Pairing Interaction in Neutron Rich A = 132 Nuclei

    SciTech Connect

    Laouet, N.; Benrachi, F.; Khiter, M.; Benmicia, N.; Saifi, H.

    2010-10-31

    In infinite nuclear systems, such as neutron stars, pairing phenomena have a particular interest in the study of nuclear structure properties. Thus, pairing lies at the heart of quantum many body problems, and nuclear process connecting to nucleosynthesis. In this work, we are interested on the contribution of this aspect, for neutron rich nuclei far from stability in the vicinity of doubly magic {sup 132}Sn. The study of A = 134 isobar, which presents a proton-neutron mixing in valence space, based on the proton-neutron correlation properties. Our results, using the P{sub d} pairing gap calculations, are in a good agreement with the experimental data.

  14. Transfer Reactions on Neutron-rich Nuclei at REX-ISOLDE

    NASA Astrophysics Data System (ADS)

    Kröll, Th.; Bildstein, V.; Wimmer, K.; Krücken, R.; Gernhäuser, R.; Lutter, R.; Schwerdtfeger, W.; Thirolf, P.; Bastin, B.; Bree, N.; Diriken, J.; Huyse, M.; Patronis, N.; Raabe, R.; Van Duppen, P.; Vermaelen, P.; Cederkäll, J.; Clément, E.; Van de Walle, J.; Voulot, D.; Wenander, F.; Blazhev, A.; Kalkühler, M.; Reiter, P.; Seidlitz, M.; Warr, N.; Deacon, A.; Fitzpatrick, C.; Freeman, S.; Das Gupta, S.; Lo Bianco, G.; Nardelli, S.; Fiori, E.; Georgiev, G.; Scheck, M.; Fraile, L. M.; Balabanski, D.; Nilsson, T.; Tengborn, E.; Butterworth, J.; Singh, B. S. Nara; Angus, L.; Chapman, R.; Hadinia, B.; Orlandi, R.; Smith, J. F.; Wady, P.; Schrieder, G.; Labiche, M.; Johansen, J.; Riisager, K.; Jeppesen, H. B.; Macchiavelli, A. O.; Davinson, T.

    2009-08-01

    We report on one- and two-neutron transfer reactions to study the single-particle properties of nuclei at the border of the "island of inversion." The (d, p)- and (t, p)-reactions in inverse kinematics on the neutron-rich isotope 30Mg, delivered as radioactive beam by the REX-ISOLDE facility, have been investigated. The outgoing protons have been detected and identified by a newly built array of Si detectors. The γ-decay of excited states has been detected in coincidence by the MINIBALL array. First results for 31Mg and from the search for the second, spherical, 0+ state in 32Mg are presented.

  15. Neutron Rich Nuclei in a New Binding Energy Formula and the Astrophysical r-PROCESS

    NASA Astrophysics Data System (ADS)

    Lahiri, Chirashree; Gangopadhyay, G.

    Neutron rich nuclei has been studied with a new phenomenological mass formula. Predictions of different mass formulas for the location of the neutron drip line are compared with those from the present calculation. The implications of the new mass formula for r-process nucleosynthesis are discussed. It is found that though the neutron drip line obtained from this formula differs substantially from other formulas, the r-process abundance upto mass 200 are unlikely to be significantly different. The errors inherent in the mass formula are found to play an insignificant role beyond mass A = 80.

  16. Thermal effects on the Fission Barrier of neutron-rich nuclei

    SciTech Connect

    Minato, Futoshi; Hagino, Kouichi

    2008-11-11

    We discuss the fission barrier height of neutron-rich nuclei in a r-process site at highly excited state, which is resulted from the beta-decay or the neutron-capture processes. We particularly investigate the sensitivity of the fission barrier height to the temperature, including the effect of pairing phase transition from superfluid to normal fluid phases. To this end, we use the finite-temperature Skyrme-Hartree-Fock-Bogolubov method with a zero-range pairing interaction. We also discuss the temperature dependence of the fission decay rate.

  17. Pygmy dipole resonances as a manifestation of the structure of the neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Tsoneva, N.; Lenske, H.; Stoyanov, Ch.

    2004-02-01

    Dipole excitations in neutron-rich nuclei below the neutron threshold are investigated. The method is based on Hartree-Fock-Bogoliubov (HFB) and Quasiparticle-Phonon Model (QPM) theory. Of our special interest are the properties of the low-lying 1 -Pygmy Resonance and the two-phonon quadrupole-octupole 1 - states in Sn-isotopes including exploratory investigations for the experimentally unknown mass regions. In particular we investigate the evolution of the dipole strength function with the neutron excess. The use of HFB mean-field potentials and s.p. energies is found to provide a reliable extrapolation into the region off stability.

  18. Structure of neutron-rich nuclei around the N = 50 shell-gap closure

    SciTech Connect

    Faul, T.; Duchene, G.; Nowacki, F.; Thomas, J.-C.; Huyse, M.; Van Duppen, P.

    2010-04-26

    The structure of neutron-rich nuclei in the vicinity of {sup 78}Ni have been investigated via the beta-decay of {sup 71,73,75}Cu isotopes (ISOLDE, CERN). Experimental results have been compared with shell-model calculations performed with the ANTOINE code using a large (2p{sub 3/2}1 f{sub 5/2}2 p{sub 1/2}1 g{sub 9/2}) valence space and a (56/28)Ni{sub 28} core.

  19. Isotopic excesses of proton-rich nuclei related to space weathering observed in a gas-rich meteorite Kapoeta

    SciTech Connect

    Hidaka, Hiroshi; Yoneda, Shigekazu E-mail: s-yoneda@kahaku.go.jp

    2014-05-10

    The idea that solar system materials were irradiated by solar cosmic rays from the early Sun has long been suggested, but is still questionable. In this study, Sr, Ba, Ce, Nd, Sm, and Gd isotopic compositions of sequential acid leachates from the Kapoeta meteorite (howardite) were determined to find systematic and correlated variations in their isotopic abundances of proton-rich nuclei, leading to an understanding of the irradiation condition by cosmic rays. Significantly large excesses of proton-rich isotopes (p-isotopes), {sup 84}Sr, {sup 130}Ba, {sup 132}Ba, {sup 136}Ce, {sup 138}Ce, and {sup 144}Sm, were observed, particularly in the first chemical separate, which possibly leached out of the very shallow layer within a few μm from the surface of regolith grains in the sample. The results reveal the production of p-isotopes through the interaction of solar cosmic rays with the superficial region of the regolith grains before the formation of the Kapoeta meteorite parent body, suggesting strong activity in the early Sun.

  20. Symmetry energy and surface properties of neutron-rich exotic nuclei

    SciTech Connect

    Gaidarov, M. K.; Antonov, A. N.; Sarriguren, P.; Moya de Guerra, E.

    2014-07-23

    The symmetry energy, the neutron pressure and the asymmetric compressibility of spherical Ni, Sn, and Pb and deformed Kr and Sm neutron-rich even-even nuclei are calculated within the coherent density fluctuation model using the symmetry energy as a function of density within the Brueckner energy-density functional. The correlation between the thickness of the neutron skin and the characteristics related with the density dependence of the nuclear symmetry energy is investigated for isotopic chains of these nuclei in the framework of the deformed self-consistent mean-field Skyrme HF+BCS method. The mass dependence of the nuclear symmetry energy and the neutron skin thickness are also studied together with the role of the neutron-proton asymmetry. The studied correlations reveal a smoother behavior in the case of spherical nuclei than for deformed ones. We also notice that the neutron skin thickness obtained for {sup 208}Pb with SLy4 force is found to be in a good agreement with the recent data. In addition to the interest that this study may have by itself, we give some numerical arguments in proof of the existence of peculiarities of the studied quantities in Ni and Sn isotopic chains that are not present in the Pb chain.

  1. Structure of Light Neutron-Rich Nuclei and Important Roles of Tensor Interaction

    SciTech Connect

    Suzuki, Toshio; Otsuka, Takaharu

    2009-08-26

    Structure of light neutron-rich nuclei are investigated by shell model calculations with the use of our new shell model Hamiltonians. The new Hamiltonians take into account important roles of the tensor interaction, and can explain well the Gamow-Teller (GT) transitions in nuclei with mass 14 and 12. A new version with repulsive corrections in T = 1 monopole terms is applied to study structure of neutron-rich carbon isotopes. Characteristics of effective neutron single particle enrgies and shell evolutions toward the drip-line are discussed. Ground state energies and low lying energy levels of the isotopes are found to be well reproduced. The anomalous quenching of the magnetic dipole (M1) transition strength in {sup 17}C is also found to be well explained. GT transitions in {sup 19}C are studied. The halo nature of {sup 19}C is investigated from a retarted GT transition. Contributions from three-nucleon forces induced by {delta} excitations are shown to be the main origin of the repulsive monopole corrections in the T = 1 channel.

  2. Nucleosynthesis of neutron-rich heavy nuclei during explosive helium burning in a 15 solar-mass supernova

    NASA Technical Reports Server (NTRS)

    Blake, J. B.; Woosley, S. E.; Weaver, T. A.; Schramm, D. N.

    1980-01-01

    The production of heavy nuclei during explosive helium burning has been calculated using the Weaver and Woosley self-consistent model of a complete 15 solar-mass star and the n-process code of Blake and Schramm. It was found that the resulting neutron-rich heavy nuclei are not produced in the relative abundances of solar-system r-process material (such as a Pt peak) nor are any actinides produced. Basically insufficient neutrons are available.

  3. Transfer Reactions on Neutron-rich Nuclei at REX-ISOLDE

    SciTech Connect

    Kroell, Th.; Bildstein, V.; Wimmer, K.; Kruecken, R.; Gernhaeuser, R.; Lutter, R.; Schwerdtfeger, W.; Thirolf, P.; Bastin, B.; Bree, N.; Diriken, J.; Huyse, M.; Patronis, N.; Raabe, R.; Van Duppen, P.; Vermaelen, P.; Cederkaell, J.; Clement, E.; Van de Walle, J.; Voulot, D.

    2009-08-26

    We report on one- and two-neutron transfer reactions to study the single-particle properties of nuclei at the border of the ''island of inversion.'' The (d, p)- and (t, p)-reactions in inverse kinematics on the neutron-rich isotope {sup 30}Mg, delivered as radioactive beam by the REX-ISOLDE facility, have been investigated. The outgoing protons have been detected and identified by a newly built array of Si detectors. The {gamma}-decay of excited states has been detected in coincidence by the MINIBALL array. First results for {sup 31}Mg and from the search for the second, spherical, 0{sup +} state in {sup 32}Mg are presented.

  4. Splitting of the isovector giant dipole resonance in neutron-rich spherical nuclei

    SciTech Connect

    Kolomietz, V.M.; Magner, A.G.; Shlomo, S.

    2006-02-15

    The well-known splitting of the isovector giant dipole resonance is traditionally explained as a phenomenon of the nuclear isospin asymmetry (isospin splitting model) or the nuclear deformation. We suggest a new mechanism of the splitting of the giant multipole resonances in spherical neutron-rich nuclei resulting from the interplay of the isovector and isoscalar sounds with different velocities. Our approach is based on the collisional Landau kinetic theory and can be used for description of the splitting phenomena for both the isoscalar and the isovector modes in a wide region of nuclear masses A{approx}40-240. For the isovector dipole modes, the evaluated values of the splitting energy, the relative strength of the main and satellite resonance peaks, and the contribution to the energy-weighted sum rule are in agreement with experimental data.

  5. Nuclear shape transitions in neutron-rich medium-mass nuclei

    SciTech Connect

    Sarriguren, P.; Rodriguez-Guzman, R.; Robledo, L. M.

    2012-10-20

    We study the isotopic evolution of the ground-state nuclear shapes in neutron-rich Kr, Rb, Sr, Y, Zr, Nb, and Mo isotopic chains. Both even-even and odd-A nuclei are included in the analysis. For the latter we also study the systematics of their one-quasiparticle low-lying configurations. The theoretical approach is based on a selfconsistent Hartree-Fock-Bogoliubov formalism with finite range Gogny energy density functionals. Neutron separation energies, charge radii, and the spin-parity of the ground states are calculated and compared with available data. Shape-transition signatures are identified around N= 60 isotones as discontinuities in both charge radii isotopic shifts and spin-parities of the ground states. The nuclear deformation including triaxiality is shown to play a relevant role in the understanding of the bulk and spectroscopic features of the ground and low-lying one-quasiparticle states.

  6. Shell structure in neutron-rich Ca and Ni nuclei under semi-realistic mean fields

    SciTech Connect

    Nakada, H.

    2010-05-15

    Shell structure in the neutron-rich Ca and Ni nuclei is investigated by the spherical Hartree-Fock calculations with semi-realistic NN interactions. Specific ingredients of the effective interaction, particularly the tensor force, often play a key role in the Z dependence of the neutron shell structure. Such examples are found in N=32 and N=40; N=32 becomes magic or submagic in {sup 52}Ca while its magicity is broken in {sup 60}Ni, and N=40 is submagic (though not magic) in {sup 68}Ni but not in {sup 60}Ca. Comments are given on the doubly magic nature of {sup 78}Ni. We point out that the loose binding can lead to a submagic number N=58 in {sup 86}Ni, assisted by the weak pair coupling.

  7. Very Low Energy Protons From the Beta Decay of Proton Rich Nuclei For Nuclear Astrophysics

    SciTech Connect

    Simmons, E.; Trache, L.; Banu, A.; McCleskey, M.; Roeder, B.; Spiridon, A.; Tribble, R. E.; Saastamoinen, A.; Aysto, J.; Davinson, T.; Woods, P. J.; Lotay, G. J.

    2010-03-01

    We have developed a new experimental technique to measure very low energy protons from beta-delayed p-decay of proton-rich nuclei produced and separated with the MARS recoil spectrometer at TAMU. Recently we have investigated the beta-delayed p-decays of {sup 23}Al and {sup 31}Cl and obtained information on the resonances in the reactions {sup 22}Na(p,gamma){sup 23}Mg and {sup 30}P(p,gamma){sup 31}S, respectively. These reactions are important in explosive H-burning in Novae. A simple setup consisting of a telescope made of a thin double sided Si strip detector (p-detector) backed or sandwiched between two thick Si detectors (beta-detectors) was designed. We studied two different p-detectors and found that the thinner detectors with a small cell size are best to measure proton energies as low as 2-300 keV.

  8. Ab initio Approach to Effective Single-Particle Energies in Doubly Closed Shell Nuclei

    SciTech Connect

    Duguet, T.

    2012-01-01

    The present work discusses, from an ab initio standpoint, the definition, the meaning, and the usefulness of effective single-particle energies (ESPEs) in doubly closed shell nuclei. We perform coupled-cluster calculations to quantify to what extent selected closed-shell nuclei in the oxygen and calcium isotopic chains can effectively be mapped onto an effective independent-particle picture. To do so, we revisit in detail the notion of ESPEs in the context of strongly correlated many-nucleon systems and illustrate the necessity of extracting ESPEs through the diagonalization of the centroid matrix, as originally argued by Baranger. For the purpose of illustration, we analyze the impact of correlations on observable one-nucleon separation energies and nonobservable ESPEs in selected closed-shell oxygen and calcium isotopes. We then state and illustrate the nonobservability of ESPEs. Similarly to spectroscopic factors, ESPEs can indeed be modified by a redefinition of inaccessible quantities while leaving actual observables unchanged. This leads to the absolute necessity of employing consistent structure and reaction models based on the same nuclear Hamiltonian to extract the shell structure in a meaningful fashion from experimental data.

  9. Octupole Deformation Bands of πh11/2 in Neutron-Rich 145,147La Nuclei

    NASA Astrophysics Data System (ADS)

    Zhu, Sheng-jiang; S, Zhu J.; Wang, Mu-ge; J, Hamilton H.; A, Ramayya V.; B, Babu R. S.; W, Ma C.; Long, Gui-lu; Zhu, Ling-yan; Li, Ming; A, Sakhaee; Gan, Cui-yun; Yang, Li-ming; J, Komicki; J, Cole D.; R, Aryaeinejad; M, Drigert W.; J, Rasmussen O.; M, Stoyer A.; S, Chu Y.; K, Gregorich E.; M, Mohar F.; S, Prussin G.; I, Lee Y.; Yu, Oganessian Ts; G, Ter-Akopian M.; A, Daniel V.

    1999-03-01

    Octupole deformation bands built on πh11/2 orbital in neutron-rich odd-Z 145,147La nuclei have been investigated by measuring the prompt γ-rays emitted from the 252Cf source. The alternating parity band structures and strong E1 transitions observed between negative- and positive-parity bands in both nuclei indicate the octupole deformation enhanced by the h11/2 single proton coupling. According to observed energy displacements the octupole deformation becomes stable at the intermediate spin states.

  10. Isomeric states observed in heavy neutron-rich nuclei populated in the fragmentation of a 208Pb beam

    NASA Astrophysics Data System (ADS)

    Steer, S. J.; Podolyák, Zs.; Pietri, S.; Górska, M.; Grawe, H.; Maier, K. H.; Regan, P. H.; Rudolph, D.; Garnsworthy, A. B.; Hoischen, R.; Gerl, J.; Wollersheim, H. J.; Becker, F.; Bednarczyk, P.; Cáceres, L.; Doornenbal, P.; Geissel, H.; Grębosz, J.; Kelic, A.; Kojouharov, I.; Kurz, N.; Montes, F.; Prokopwicz, W.; Saito, T.; Schaffner, H.; Tashenov, S.; Heinz, A.; Pfützner, M.; Kurtukian-Nieto, T.; Benzoni, G.; Jungclaus, A.; Balabanski, D. L.; Bowry, M.; Brandau, C.; Brown, A.; Bruce, A. M.; Catford, W. N.; Cullen, I. J.; Dombrádi, Zs.; Estevez, M. E.; Gelletly, W.; Ilie, G.; Jolie, J.; Jones, G. A.; Kmiecik, M.; Kondev, F. G.; Krücken, R.; Lalkovski, S.; Liu, Z.; Maj, A.; Myalski, S.; Schwertel, S.; Shizuma, T.; Walker, P. M.; Werner-Malento, E.; Wieland, O.

    2011-10-01

    Heavy neutron-rich nuclei were populated via the fragmentation of a E/A=1 GeV 20882Pb beam. Secondary fragments were separated and identified and subsequently implanted in a passive stopper. By the detection of delayed γ rays, isomeric decays associated with these nuclei have been identified. A total of 49 isomers were detected, with the majority of them observed for the first time. The newly discovered isomers are in 204,20580Hg, 201,202,204,20579Au, 197,203,20478Pt, 195,199-20377Ir, 193,197-19976Os, 19675Re, 190,19174W, and 18973Ta. Possible level schemes are constructed and the structure of the nuclei discussed. To aid the interpretation, shell-model as well as BCS calculations were performed.

  11. Stability of proton-rich nuclei in the upper {ital sd} shell and lower {ital pf} shell

    SciTech Connect

    Cole, B.J.

    1996-09-01

    The decay properties of proton-rich nuclei with {ital Z}=19{endash}30 are investigated using measured binding energies of the analog neutron-rich nuclei and Coulomb energy shifts deduced from a parametrization of measured Coulomb displacement energies. Predicted binding energies and separation energies are compared where possible with previous calculations; in most cases the calculations agree within the quoted uncertainties. The positions of the one-proton and diproton drip lines are determined from the calculated separation energies. It is suggested that good candidates for the observation of correlated two-proton emission are {sup 34}Ca, {sup 38,39}Ti, {sup 45}Fe, {sup 48}Ni, and {sup 54}Zn. {copyright} {ital 1996 The American Physical Society.}

  12. Precision Mass Measurements of Short-Lived, Neutron-Rich, R-Process Nuclei About the N=82 Waiting Point

    NASA Astrophysics Data System (ADS)

    Lascar, Daniel David

    This thesis details the precision mass measurements of 33 neutron-rich ground-state nuclei and isomeric states that approach or lie on the proposed rapid neutron capture process (r-process) path. For many of the nuclei measured the work presented here will be the rst direct mass measurements of these nuclei, including 130In, 137Sb, 133I, and 134I. The measurements were made using the Canadian Penning Trap mass spectrometer (CPT), located at the ATLAS heavy ion-linac at Argonne National Laboratory. Ground states and isomers have been measured with the CPT at fractional precisions (δm/m) between 10-7, and 10-8. The nuclei were produced at the new CAlifornium Rare Isotope Breeder Upgrade (CARIBU) to ATLAS. Because nuclear masses are required for measuring neutron separation energies, and neutron separation energies are important inputs in r-process network calculations, precision mass measurements are critical for advancing our knowledge of the r-process. This thesis will give the astrophysical motivation for making these mass measurements, the theoretical background behind ion trapping and mass measurements using ion traps, an explanation of the CPT apparatus, the mass measurements themselves, and the results of those measurements as they pertain to r-process network calculations. Results of these mass measurements show significant shifts in the r-process path over a range of temperatures and neutron densities.

  13. A New Island of Inversion Far From Stability: Structure of Neutron-Rich Nuclei Near N = 40

    SciTech Connect

    Lenzi, Silvia M.

    2010-08-04

    Recent results obtained for neutron-rich nuclei of mass A{approx}60-70 are presented together with the theoretical interpretation. The development of a new region of deformation approaching the neutron number N = 40 in Cr and Fe isotopes is discussed. A new effective interaction that considers the full fp shell model space for protons and the p{sub 3/2}, p{sub 1/2}, f{sub 5/2}, g{sub 9/2}, d{sub 5/2} orbitals for the neutrons allows to reproduce, for the first time, the different structure properties of these nuclei. The configuration of the calculated states suggests the development of a new island of inversion at N{approx}40. The perspectives offered by the forthcoming operation of the AGATA Demonstrator Array coupled to the magnetic spectrometer PRISMA at LNL are also discussed.

  14. Crossings in alternating-parity bands of neutron-rich Ba nuclei

    SciTech Connect

    Urban, W.; Jones, M.A.; Durell, J.L.

    1995-07-22

    {sup 144}Ba and {sup 146}Ba nuclei produced in the spontaneous fission of {sup 248}Cm have been studied using the EUROGRAM II array. Spins and parities of excited levels have been deduced from triple-{gamma} angular correlation and direction-polarization correlation measurements, which is the first use of these techniques in studies of fission product nuclei. Ground-state, alternating-parity bands have been extended significantly and crossing in these bands has been found in both isotopes. For the first time alternating-parity band termination by particle alignment has been observed.

  15. Survivability and Fusability in Reactions Leading to Heavy Nuclei in the Vicinity of the N = 126 Closed Shell

    SciTech Connect

    Sagaidak, Roman N.

    2009-08-26

    The macroscopic component of fission barriers for Po to Th nuclei around the N = 126 closed neutron shell has been derived within the framework of the analysis of available fission and evaporation residues excitation functions using the conventional barrier passing (fusion) model coupled with the standard statistical model and compared with the predictions of various theoretical models.

  16. β-Decay of Neutron-Rich Nuclei around 158Nd and the Origin of Rare-Earth Elements

    NASA Astrophysics Data System (ADS)

    Wu, J.; Nishimura, S.; Lorusso, G.; Xu, Z. Y.; Ideguchi, E.; Simpson, G. S.; Baba, H.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y. F.; Isobe, T.; Li, Z.; Patel, Z.; Rice, S.; Sinclair, L.; Söderström, P.-A.; Sumikama, T.; Watanabe, H.; Yagi, A.; Yokoyama, R.; Aoi, N.; Bello Garrote, F. L.; Benzoni, G.; Gey, G.; Gottardo, A.; Nishibata, H.; Odahara, A.; Sakurai, H.; Tanaka, M.; Taprogge, J.; Yamamoto, T.

    A large fraction of the rare-earth elements around mass number A = 160 observed in the solar system are produced in the astrophysical rapid (r-) neutron capture process. However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a β-decay spectroscopy experiment was performed at the RI Beam Factory (RIBF), aimed at studying a wide region of very neutron-rich nuclei around 158Nd. The data from this experiment provides a test of nuclear models as well as experimental inputs for r-process calculations.

  17. Masses of proton-rich T/sub z/<0 nuclei via the isobaric mass equation

    SciTech Connect

    Pape, A.; Antony, M.S.

    1988-07-01

    Masses of T/sub z/<0 nuclei through the element Sm, corresponding to Aless than or equal to117, have been calculated with the isobaric multiplet mass equation using parameterizations of its constant b and T/sub z/>0 reference masses of Wapstra, Audi, and Hoekstra. copyright 1988 Academic Press, Inc.

  18. The Sensitivity of r-PROCESS Nucleosynthesis to the Properties of Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Surman, R.; Mumpower, M. R.; Cass, J.; Aprahamian, A.

    2014-09-01

    About half of the heavy elements in the Solar System were created by rapid neutron capture, or r-process, nucleosynthesis. In the r-process, heavy elements are built up via a sequence of neutron captures and beta decays in which an intense neutron flux pushes material out towards the neutron drip line. The nuclear network simulations used to test potential astrophysical scenarios for the r-process therefore require nuclear physics data (masses, beta decay lifetimes, neutron capture rates, fission probabilities) for thousands of nuclei far from stability. Only a small fraction of this data has been experimentally measured. Here we discuss recent sensitivity studies that aim to determine the nuclei whose properties are most crucial for r-process calculations.

  19. Novel triaxial structure in low-lying states of neutron-rich nuclei around A ≈100

    NASA Astrophysics Data System (ADS)

    Xiang, J.; Yao, J. M.; Fu, Y.; Wang, Z. H.; Li, Z. P.; Long, W. H.

    2016-05-01

    Background: In recent years, the study of triaxiality in the low-lying states of atomic nuclei with transition character or shape coexistence has been of great interest. Previous studies indicate that the neutron-rich nuclei in the A ˜100 mass region with Z ˜40 ,N ˜60 serve as good grounds for examining the role of triaxiality in nuclear low-lying states. Purpose: The aim of this work is to provide a microscopic study of low-lying states for nuclei in the A ˜100 mass regions and to examine in detail the role of triaxiality in the shape-coexistence phenomena and the variation of shape with the isospin and spin values at the beyond mean-field level. Method: The starting point of our method is a set of relativistic mean-field plus BCS wave functions generated with a constraint on triaxial deformations (β ,γ ) . The excitation energies and electric multipole transition strengths of low-lying states are calculated by solving a five-dimensional collective Hamiltonian (5DCH) with parameters determined by the mean-field wave functions. Results: The low-lying states of Mo isotopes and of N =60 isotones in the A ˜100 mass region are calculated. The results indicate that triaxiality is essential to reproduce the data of excitation energies and electric quadrupole transition strengths in low-lying states and plays an important role in the shape evolution as a function of nucleon number. However, the decrease of nuclear collectivity with the increase of angular momentum in neutron-rich Mo isotopes has not been reproduced. Conclusions: The evolution of nuclear collectivity in the low-lying states of neutron-rich nuclei in the A ˜100 mass region as a function of nucleon number is governed by the novel triaxial structure. However, the mechanism that governs the variation of nuclear shape with spin in Mo isotopes remains unclear and deserves further investigation by taking into account the effects other than the collective motions.

  20. Exploring Light Neutron Rich Nuclei via the ({sup 7}Li,{sup 7}Be) Reaction

    SciTech Connect

    Cavallaro, M.; Cappuzzello, F.; Cunsolo, A.; Foti, A.; Orrigo, S. E. A.; Rodrigues, M. R. D.; Borello-Lewin, T.; Lenske, H.; Petrascu, H.; Winfield, J. S.

    2008-11-11

    A systematic study of the nuclei that can be described as an integer number of {alpha} particles plus three neutrons via the ({sup 7}Li,{sup 7}Be) reaction at about 8 MeV/u has shown the presence of Bound States Embedded in the Continuum in the energy spectra. These are experimental signatures of the dynamical correlations of an easily polarizable core with a single-particle state of the valence neutron.

  1. Constrained Hartree-Fock Theory and Study of Deformed Structures of Closed Shell Nuclei

    NASA Astrophysics Data System (ADS)

    Praharaj, Choudhury

    2016-03-01

    We have studied some N or Z = 50 nuclei in a microscopic model with effective interaction in a reasonably large shell model space. Excitation of particles across 50 shell closure leads to well-deformed excited prolate configurations. The potential energy surfaces of nuclei are studied using Hartree-Fock theory with quadrupole constraint to explore the various deformed configurations of N = 50 nuclei 82Ge , 84Se and 86Kr . Energy spectra are calculated from various intrinsic states using Peierls-Yoccoz angular momentum projection technique. Results of spectra and electromagnetic moments and transitions will be presented for N = 50 nuclei and for Z = 50 114Sn nucleus. Supported by Grant No SB/S2/HEP-06/2013 of DST.

  2. Production of beams of neutron-rich nuclei between Ca and Ni using the ion-guide technique

    SciTech Connect

    Perajarvi, K.; Cerny, J.; Hager, U.; Hakala, J.; Huikari, J.; Jokinen, A.; Karvonen, P.; Kurpeta, J.; Lee, D.; Moore, I.; Penttila, H.; Popov, A.; Aysto, J.

    2004-09-28

    Since several elements between Z = 20-28 are refractory in their nature, their neutron-rich isotopes are rarely available as low energy Radioactive Ion Beams (RIB) in ordinary Isotope Separator On-Line facilities [1-4]. These low energy RIBs would be especially interesting to have available under conditions which allow high-resolution beta-decay spectroscopy, ion-trapping and laser-spectroscopy. As an example, availability of these beams would open a way for research which could produce interesting and important data on neutron-rich nuclei around the doubly magic {sup 78}Ni. One way to overcome the intrinsic difficulty of producing these beams is to rely on the chemically unselective Ion Guide Isotope Separator On-Line (IGISOL) technique [5]. Quasi- and deep-inelastic reactions, such as {sup 197}Au({sup 65}Cu,X)Y, could be used to produce these nuclei in existing IGISOL facilities, but before they can be successfully incorporated into the IGISOL concept their kinematics must be well understood. Therefore the reaction kinematics part of this study was first performed at the Lawrence Berkeley National Laboratory using its 88'' cyclotron and, based on those results, a specialized target chamber was built[6]. The target chamber shown in Fig. 1 was recently tested on-line at the Jyvaaskylaa IGISOL facility. Yields of mass-separated radioactive projectile-like species such as {sup 62,63}Co are about 0.8 ions/s/pnA, corresponding to about 0.06 % of the total IGISOL efficiency for the products that hit the Ni-degrader. (The current maximum 443 MeV {sup 65}Cu beam intensity at Jyvaaskylaa is about 20 pnA.) This total IGISOL efficiency is a product of two coupled loss factors, namely inadequate thermalization and the intrinsic IGISOL efficiency. In our now tested chamber, about 9 % of the Co recoils are thermalized in the owing He gas (p{sub He}=300 mbar) and about 0.7 % of them are converted into the mass-separated ion beams. In the future, both of these physical

  3. Fragmentation cross sections and binding energies of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Tsang, M. B.; Lynch, W. G.; Friedman, W. A.; Mocko, M.; Sun, Z. Y.; Aoi, N.; Cook, J. M.; Delaunay, F.; Famiano, M. A.; Hui, H.; Imai, N.; Iwasaki, H.; Motobayashi, T.; Niikura, M.; Onishi, T.; Rogers, A. M.; Sakurai, H.; Suzuki, H.; Takeshita, E.; Takeuchi, S.; Wallace, M. S.

    2007-10-01

    An exponential dependence of the fragmentation cross section on the average binding energy is observed and reproduced with a statistical model. The observed functional dependence is robust and allows the extraction of binding energies from measured cross sections. From the systematics of Cu isotope cross sections, the binding energies of Cu76,77,78,79 have been extracted. They are 636.94±0.4,647.1±0.4,651.6±0.4, and 657.8±0.5 MeV, respectively. Specifically, the uncertainty of the binding energy of Cu75 is reduced from 980 keV, as listed in the 2003 mass table of Audi, Wapstra, and Thibault to 400 keV. The predicted cross sections of two near drip-line nuclei, Na39 and Mg40 from the fragmentation of Ca48 are discussed.

  4. Fragmentation cross sections and binding energies of neutron-rich nuclei

    SciTech Connect

    Tsang, M. B.; Lynch, W. G.; Mocko, M.; Cook, J. M.; Delaunay, F.; Famiano, M. A.; Hui, H.; Rogers, A. M.; Wallace, M. S.; Friedman, W. A.; Sun, Z. Y.; Aoi, N.; Imai, N.; Motobayashi, T.; Takeuchi, S.; Iwasaki, H.; Onishi, T.; Sakurai, H.; Suzuki, H.; Niikura, M.

    2007-10-15

    An exponential dependence of the fragmentation cross section on the average binding energy is observed and reproduced with a statistical model. The observed functional dependence is robust and allows the extraction of binding energies from measured cross sections. From the systematics of Cu isotope cross sections, the binding energies of {sup 76,77,78,79}Cu have been extracted. They are 636.94{+-}0.4,647.1{+-}0.4,651.6{+-}0.4, and 657.8{+-}0.5 MeV, respectively. Specifically, the uncertainty of the binding energy of {sup 75}Cu is reduced from 980 keV, as listed in the 2003 mass table of Audi, Wapstra, and Thibault to 400 keV. The predicted cross sections of two near drip-line nuclei, {sup 39}Na and {sup 40}Mg from the fragmentation of {sup 48}Ca are discussed.

  5. β-decay of neutron-rich Zâ¼60 nuclei and the origin of rare earth elements

    NASA Astrophysics Data System (ADS)

    Wu, J.; Nishimura, S.; Lorusso, G.; Xu, Z. Y.; Baba, H.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y. F.; Ideguchi, E.; Isobe, T.; Li, Z.; Patel, Z.; Rice, S.; Simpson, G.; Sinclair, L.; Söderström, P. A.; Sumikama, T.; Watanabe, H.; Yagi, A.; Yokoyama, R.; Aoi, N.; Garrote, F. L. Bello; Benzoni, G.; Gey, G.; Gottardo, A.; Nishibata, H.; Odahara, A.; Sakurai, H.; Tanaka, M.; Taprogge, J.; Yamamoto, T.; Eurica Collaboration

    2014-05-01

    A large fraction of the rare-earth elements observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a β-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z˜60 that are progenitors of the rare-earth elements with mass number A˜460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.

  6. β-decay of neutron-rich Z∼60 nuclei and the origin of rare earth elements

    SciTech Connect

    Wu, J.; Nishimura, S.; Lorusso, G.; Baba, H.; Doornenbal, P.; Isobe, T.; Söderström, P. A.; Sakurai, H.; Xu, Z. Y.; Browne, F.; Daido, R.; Fang, Y. F.; Yagi, A.; Nishibata, H.; Odahara, A.; Yamamoto, T.; Ideguchi, E.; Aoi, N.; Tanaka, M.; Collaboration: EURICA Collaboration; and others

    2014-05-02

    A large fraction of the rare-earth elements observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a β-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z∼60 that are progenitors of the rare-earth elements with mass number A∼460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.

  7. Continuum quasiparticle random-phase approximation for astrophysical direct neutron capture reactions on neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Matsuo, Masayuki

    2015-03-01

    I formulate a many-body theory to calculate the cross section of direct radiative neutron capture reaction by means of the Hartree-Fock-Bogoliubov mean-field model and the continuum quasiparticle random-phase approximation (QRPA). A focus is put on very-neutron-rich nuclei and low-energy neutron kinetic energy in the range from 1 keV to several MeV, which is relevant to the rapid neutron capture process of nucleosynthesis. I begin with the photoabsorption cross section and the E 1 strength function. Next, in order to apply the reciprocity theorem, I decompose the cross section into partial cross sections corresponding to different channels of one- and two-neutron emission decays of photo-excited states. A numerical example is shown for the photo-absorption of 142Sn and the neutron capture of 141Sn .

  8. Effect of finite range of the NN force and NN cross section on reaction cross section for neutron rich nuclei

    SciTech Connect

    Ismail, M.; Ellithi, A.Y.; Abou-Shady, H.

    2005-02-01

    The reaction cross section ({sigma}{sub R}) is calculated using the optical limit of the Glauber theory. A density-dependent effective nucleon-nucleon (NN) cross section {sigma}{sub NN} is considered. Finite and zero range NN interactions are studied. The effect of finite range and an appropriate local density can increase {sigma}{sub R} up to 20% compared to the zero range at constant density (0.16 fm{sup -3}), while a zero range calculation with free NN cross section increases {sigma}{sub R} up to 13%. These factors affect the values of the rms radii for neutron rich nuclei extracted from {sigma}{sub R}.

  9. Beta-Decay and Delayed Neutron Emission of Very Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Borzov, I. N.

    2014-09-01

    Extended self-consistent beta-decay model has been applied for beta-decay rates and delayed multi-neutron emission probabilities of quasi-spherical neutron-rich isotopes. The Gamow-Teller and first-forbidden decays are treated within the coordinate-space formalism of the continuum QRPA based on the density functional theory description of the ground state. A new set of the Fayans density functional parameters (DF3a) have been employed giving a better spin-orbit splitting due to a stronger tensor term. A provision has been included to fix the odd particle in the proper orbit (before variation). This accounts for ground-state spin inversion effect which has been shown to exist in the region of the most neutron-rich doubly-magic nucleus 78Ni.

  10. β -decay half-lives of neutron-rich nuclei at A ~ 110 on r-process path

    NASA Astrophysics Data System (ADS)

    Nishizuka, Ippei; Sumikama, Toshiyuki; Browne, Frank; Bruce, Alison; Nishimura, Shunji; Doornenbal, Pieter; Lorusso, Giuseppe; Patel, Zena; Rice, Simon; Sinclair, Laura; Soderstom, Par-Ander; Watanabe, Hiroshi; Wu, Jin; Xu, Zhengyu; Yagi, Ayumi; Eurica Collaboration

    2014-09-01

    About half of the elements heavier than iron are thought to be produced by rapid-neutron capture process (r-process). The observed natural abundance in solar system was underestimated by a theoretical model at A ~ 110 , which uses β-decay half-lives. In the present study, we measured new β half-lives of neutron-rich nuclei on r-process path at RIBF in RIKEN. The nuclei of interest were produced by in-flight fission of uranium beam in beryllium target. The WAS3ABi detector which was 5 stacked double-sided silicon strip detectors (60 × 40 × 1 mm3), was used for the implantation of ions and the detection of both the implanted ions and the subsequently-emitted β rays. It is essential to make a position correlation between the mother nucleus and the β rays. In this talk, the analysis of the position correlation will be presented in detail. Preliminary results will be also shown.

  11. Interaction radii of proton-rich radioactive nuclei at A=60-80

    SciTech Connect

    Lima, G. F.; Lepine-Szily, A.; Lichtenthaler, R.; Villari, A. C. C.; Mittig, W.; Casandjian, J. M.; Lewitowicz, M.; Chartier, M.; Hirata, D.; Angelique, J. C.; Orr, N. A.; Audi, G.; Cunsolo, A.; Foti, A.; Donzeaud, C.; MacCormick, M.; Stephan, C.; Suomijarvi, T.; Tassan-Got, L.; Gillibert, A.

    1998-12-21

    The interaction radii of proton-rich, radioactive {sub 31}Ga, {sub 32}Ge, {sub 33}As, {sub 34}Se, {sub 35}Br isotopes were measured using the direct method. The secondary beams were produced using a {sup 78}Kr primary beam of 73 MeV/nucleon in conjunction with SISSI and the SPEG spectrometers at GANIL. Most elements show reduced radii which vary with N, with a minimum around N=36-38. The experimental reduced radii are compared to theoretical values obtained from Glauber reaction cross-section calculations based on Relativistic Mean Field (RMF) nuclear densities.

  12. Neutron-Rich Nuclei Beyond {sup 132}Sn: Spherical Shapes and Octupole Correlations

    SciTech Connect

    Liu Shaohua; Hamilton, Joseph H.; Ramayya, Akunuri V.; Goodin, Christopher T.; Hwang, Jae-Kwang; Luo Yixiao; Rasmussen, John O.; Covello, Aldo; Gargano, Angel; Stone, Nick J.; Daniel, Andrey V.; Ter-Akopian, Gurgen M.; Oganessian, Yuri Ts.; Zhu Shengjiang

    2010-04-30

    Nuclear properties of nuclei with a few valence nucleons outside the doubly-magic {sup 132}Sn core and located in the octupole correlation region have been investigated via gamma-gamma-gamma coincidence measurements of prompt gamma-ray emitted in the spontaneous fission of {sup 252}Cf with Gammasphere. The high spin level scheme of {sup 134}I has been identified for the first time. Shell model calculations reproduce the level scheme quite well. The level schemes of {sup 137}I and {sup 139}Cs have been reinvestigated and extended. Their nuclear structure is well described by realistic shell model calculations. The g-factors of the 4{sup +} state in {sup 134}Te, 15/2{sup +} state in {sup 135}I, and 15/2{sup -} state in {sup 137}Xe were determined using a newly developed program for angular correlation analysis. The measured g-factors compared favorably with shell model calculations. Octupole correlations are proposed in {sup 141}Cs and {sup 142}Cs. The variations of D{sub 0} in the Cs isotopes exhibit a pronounced drop of dipole moment with increasing neutron number.

  13. Charge-exchange modes of excitation in deformed neutron-rich nuclei

    SciTech Connect

    Yoshida, Kenichi

    2015-10-15

    Gamow-Teller (GT) mode of excitation and β-decay properties of deformed neutron-rich even-N Zr isotopes are investigated in a self-consistent Skyrme energy-density-functional approach, in which the Hartree-Fock-Bogoliubov equation is solved in the coordinate space and the proton-neutron Quasiparticle-RPA equation is solved in the quasiparticle basis. It is found that a stronger collectivity is generated for the GT giant resonance as an increase in the neutron number. Furthermore, we find that the T = 0 pairing enhances the low-lying GT strengths cooperatively with the T = 1 pairing correlation depending on the microscopic structure of the low-lying mode and the shell structure around the Fermi levels, and that the enhanced strength shortens the β-decay half-lives by at most an order of magnitude.

  14. Interaction radii of proton-rich radioactive nuclei at A=60{endash}80

    SciTech Connect

    Lima, G.F.; Lepine-Szily, A.; Villari, A.C.; Lichtenthaler, R.; Villari, A.C.; Mittig, W.; Chartier, M.; Casandjian, J.M.; Lewitowicz, M.; Ostrowski, A.N.; Hirata, D.; Angelique, J.C.; Orr, N.A.; Audi, G.; Cunsolo, A.; Foti, A.; Donzeaud, C.; MacCormick, M.; Stephan, C.; Suomijarvi, T.; Tassan-Got, L.; Gillibert, A.; Chartier, M.; Morrissey, D.J.; Sherrill, B.M.; Ostrowski, A.N.; Vieira, D.J.; Wouters, J.M.

    1998-12-01

    The interaction radii of proton-rich, radioactive {sub 31}Ga,thinsp{sub 32}Ge,thinsp{sub 33}As,thinsp{sub 34}Se,thinsp{sub 35}Br isotopes were measured using the direct method. The secondary beams were produced using a {sup 78}Kr primary beam of 73 MeV/nucleon in conjunction with SISSI and the SPEG spectrometers at GANIL. Most elements show reduced radii which vary with N, with a minimum around N=36{endash}38. The experimental reduced radii are compared to theoretical values obtained from Glauber reaction cross-section calculations based on Relativistic Mean Field (RMF) nuclear densities. {copyright} {ital 1998 American Institute of Physics.}

  15. The neutron skin in neutron-rich nuclei at Jefferson Lab

    SciTech Connect

    Dalton, Mark M.

    2013-11-01

    The Jefferson Lab program to measure the symmetry energy of neutron-rich nuclear matter, using precision electroweak methods, is progressing well. The initial measurement by the PREX experiment, leading to a 2-sigma determination of the "neutron skin" in {sup 208}Pb , has been published. Design and preparation for a further, more-precise measurement on {sup 208}Pb is progressing well and there is general acceptance of the great advantage to a further measurement on {sup 48}Ca . The surprising ancillary result that the beam-normal single-spin asymmetry for {sup 208}Pb is consistent with zero is also now in the literature. This paper will discuss the current experimental situation of the program.

  16. The neutron skin in neutron-rich nuclei at Jefferson Lab

    SciTech Connect

    Dalton, Mark M.

    2013-11-07

    The Jefferson Lab program to measure the symmetry energy of neutron-rich nuclear matter, using precision electroweak methods, is progressing well. The initial measurement by the PREX experiment, leading to a 2-sigma determination of the 'neutron skin' in {sup 208}Pb, has been published. Design and preparation for a further, more-precise measurement on {sup 208}Pb is progressing well and there is general acceptance of the great advantage to a further measurement on {sup 48}Ca. The surprising ancillary result that the beam-normal single-spin asymmetry for {sup 208}Pb is consistent with zero is also now in the literature. This paper will discuss the current experimental situation of the program.

  17. Schottky Mass Measurements of Cooled Proton-Rich Nuclei at the GSI Experimental Storage Ring

    SciTech Connect

    Radon, T.; Schlitt, B.; Beckert, K.; Bosch, F.; Eickhoff, H.; Franzke, B.; Geissel, H.; Hausmann, M.; Irnich, H.; Klepper, O.; Kluge, H.; Kozhuharov, C.; Kraus, G.; Muenzenberg, G.; Nickel, F.; Nolden, F.; Patyk, Z.; Reich, H.; Scheidenberger, C.; Schwab, W.; Steck, M.; Suemmerer, K.; Kerscher, T.; Beha, T.; Loebner, K.E.; Fujita, Y.; Jung, H.C.; Wollnik, H.; Novikov, Y.

    1997-06-01

    High-precision mass measurements of proton-rich isotopes in the range of 60{le}Z{le}84 were performed using the novel technique of Schottky spectrometry. Projectile fragments produced by {sup 209}Bi ions at 930{ital A} MeV were separated with the magnetic spectrometer FRS and stored and cooled in the experimental storage ring (ESR). A typical mass resolving power of 350000 and a precision of 100keV were achieved in the region A{approx}200 . Masses of members of {alpha} chains linked by precise Q{sub {alpha}} values but not yet connected to the known masses were determined. In this way it is concluded that {sup 201}Fr and {sup 197}At are proton unbound. {copyright} {ital 1997} {ital The American Physical Society}

  18. Synthesis of neutron-rich transuranic nuclei in fissile spallation targets

    NASA Astrophysics Data System (ADS)

    Mishustin, Igor; Malyshkin, Yury; Pshenichnov, Igor; Greiner, Walter

    2015-04-01

    A possibility of synthesizing neutron-rich superheavy elements in spallation targets of Accelerator Driven Systems (ADS) is considered. A dedicated software called Nuclide Composition Dynamics (NuCoD) was developed to model the evolution of isotope composition in the targets during a long-time irradiation by intense proton and deuteron beams. Simulation results show that transuranic elements up to 249Bk can be produced in multiple neutron capture reactions in macroscopic quantities. However, the neutron flux achievable in a spallation target is still insufficient to overcome the so-called fermium gap. Further optimization of the target design, in particular, by including moderating material and covering it by a reflector could turn ADS into an alternative source of transuranic elements in addition to nuclear fission reactors.

  19. Beta-decay properties of neutron-rich medium-mass nuclei

    NASA Astrophysics Data System (ADS)

    Sarriguren, Pedro

    2016-06-01

    β-decay properties of even-even and odd-A neutron-rich Ge, Se, Kr, Sr, Zr, Mo, Ru, and Pd isotopes involved in the astrophysical rapid neutron capture process are studied within a microscopic proton-neutron quasiparticle random-phase approximation. The underlying mean field is based on a self-consistent Skyrme Hartree-Fock + BCS calculation that includes deformation as a key ingredient. The isotopic evolution of the various nuclear equilibrium shapes and the corresponding charge radii are investigated in all the isotopic chains. The energy distributions of the Gamow-Teller strength, as well as the β-decay half-lives are discussed and compared with the available experimental information. It is shown that nuclear deformation plays a significant role in the description of the decay properties in this mass region. Reliable predictions of the strength distributions are essential to evaluate decay rates in astrophysical scenarios.

  20. Precision mass measurements of neutron-rich nuclei, and limitations on the r-process environment

    NASA Astrophysics Data System (ADS)

    Van Schelt, Jonathon A.

    2012-05-01

    The masses of 65 neutron-rich nuclides and 6 metastable states from Z = 49 to 64 were measured at a typical precision of δm/m= 10-7 using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements are on fission fragments from 252Cf spontaneous fission sources, including those measurements made at the new Californium Rare Isotope Breeder Upgrade facility (CARIBU) and an earlier source. The measured nuclides lie on or approach the predicted path of the astrophysical r process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in β-endpoint measurements. Simulations of the r process were undertaken to determine how quickly material can pass through the studied elements for a variety of conditions, placing limits on what temperatures densities allow passage on a desired timescale. The new masses produce manifold differences in effective lifetime compared to simulations performed with some model masses.

  1. Closed formulas for ground band energies of nuclei with various symmetries

    NASA Astrophysics Data System (ADS)

    Raduta, A. A.; Budaca, R.; Faessler, Amand

    2010-08-01

    A time-dependent variational principle is used to dequantize a second-order quadrupole boson Hamiltonian. The classical equations for the generalized coordinate and the constraint for the angular momentum are quantized and then analytically solved. A generalized Holmberg-Lipas formula for energies is obtained. A similar J(J + 1) dependence is provided by the coherent state model in the large deformation regime, by using an expansion in powers of 1/x for energies, with x denoting a deformation parameter squared. A simple compact expression is also possible for the near-vibrational regime. These three expressions have been used for 44 nuclei covering regions characterized by different dynamic symmetries or in other words belonging to all the known nuclear phases. Nuclei satisfying the specific symmetries of the critical point in the phase transitions O(6) → SU(3), SU(5) → SU(3) have also been considered. The agreement between the results and the corresponding experimental data is very good. This is reflected in very small root mean square values of deviations.

  2. Dineutron correlations in quasi-two-dimensional systems in a simplified model, and possible relation to neutron-rich nuclei

    SciTech Connect

    Kanada-En'yo, Yoshiko; Hinohara, Nobuo; Suhara, Tadahiro; Schuck, Peter

    2009-05-15

    Two-neutron correlation in the {sup 1}S channel in quasi-two-dimensional (2D) neutron systems at zero temperature is studied by means of the BCS theory with finite-range effective nuclear forces. The dineutron correlation in low density neutron systems confined in an infinite slab is investigated in a simplified model that neutron motion of one direction is frozen. When the slab is thin enough, two neutrons form a tightly bound dineutron with a small size in the quasi-2D system, and a Bose dineutron gas is found in low density limit. With increase of Fermi momentum, the neutron system changes from the Bose-gas phase to the superfluid Cooper pair phase. The density dependence of the neutron pairing shows the BCS-BEC crossover phenomena at finite low-density region. In the transition region, the size shrinking of neutron pair and enhancement of pairing gap are found. The relation to dineutron correlation at surface of neutron-rich nuclei is also discussed.

  3. High-K isomers in transactinide nuclei close to N = 162

    SciTech Connect

    Prassa, V. Nikšić, T.; Vretenar, D.; Lu, Bing-Nan; Ackermann, D.

    2015-10-15

    Transactinide nuclei around neutron number N = 162 display axially deformed equilibrium shapes, as shown in our previous analysis [1] of constrained mean-field energy surfaces and collective excitation spectra. In the present study we are particularly interested in the occurrence of high-K isomers in the axially deformed isotopes of Rf (Z = 104), Sg (Z = 106), Hs (Z = 108), and Ds (Z = 110), with neutron number N = 160 − 166 and the effect of the N=162 closure on the structure and distribution of two-quasiparticle (2qp) states. The evolution of high-K isomers is analysed in a self-consistent axially-symmetric relativistic Hartree-Bogoliubov calculation using the blocking approximation with time-reversal symmetry breaking.

  4. Half-life systematics across the N=126 shell closure: role of first-forbidden transitions in the β decay of heavy neutron-rich nuclei.

    PubMed

    Morales, A I; Benlliure, J; Kurtukián-Nieto, T; Schmidt, K-H; Verma, S; Regan, P H; Podolyák, Z; Górska, M; Pietri, S; Kumar, R; Casarejos, E; Al-Dahan, N; Algora, A; Alkhomashi, N; Álvarez-Pol, H; Benzoni, G; Blazhev, A; Boutachkov, P; Bruce, A M; Cáceres, L S; Cullen, I J; Denis Bacelar, A M; Doornenbal, P; Estévez-Aguado, M E; Farrelly, G; Fujita, Y; Garnsworthy, A B; Gelletly, W; Gerl, J; Grebosz, J; Hoischen, R; Kojouharov, I; Kurz, N; Lalkovski, S; Liu, Z; Mihai, C; Molina, F; Mücher, D; Rubio, B; Shaffner, H; Steer, S J; Tamii, A; Tashenov, S; Valiente-Dobón, J J; Walker, P M; Wollersheim, H J; Woods, P J

    2014-07-11

    This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic (208)Pb. The lifetimes of the 126-neutron shell isotone (204)Pt and the neighboring (200-202)Ir, (203)Pt, (204)Au are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first-forbidden transitions reproduce more satisfactorily the trend in the measured half-lives for the nuclei in this region, where the r-process pathway passes through during β decay back to stability. PMID:25062171

  5. Pygmy dipole response of proton-rich argon nuclei in random-phase approximation and no-core shell model

    SciTech Connect

    Barbieri, C.; Martinez-Pinedo, G.; Caurier, E.; Langanke, K.

    2008-02-15

    The occurrence of a pygmy dipole resonance in proton rich {sup 32,34}Ar is studied using the unitary correlator operator method interaction V{sub UCOM}, based on Argonne V18. Predictions from the random-phase approximation (RPA) and the shell model in a no-core basis are compared. It is found that the inclusion of configuration mixing up to two-particles-two-holes broadens the pygmy strength slightly and reduces sensibly its strength, as compared to the RPA predictions. For {sup 32}Ar, a clear peak associated with a pygmy resonance is found. For {sup 34}Ar, the pygmy states are obtained close to the giant dipole resonance and mix with it.

  6. Three active galactic nuclei close to the effective Eddington limit for dusty gas

    NASA Astrophysics Data System (ADS)

    Vasudevan, R. V.; Fabian, A. C.; Mushotzky, R. F.; Meléndez, M.; Winter, L. M.; Trippe, M. L.

    2013-06-01

    The effective Eddington limit for dusty gas surrounding active galactic nucleus (AGN) is lower than the canonical Eddington limit for hydrogen gas. Previous results from the Swift/Burst Alert Telescope 9-month catalogue suggested that in the overwhelming majority of local AGN, the dusty absorbing gas is below this effective Eddington limit, implying that radiation pressure is insufficient to blow away the absorbing clouds. We present an analysis of three objects from that sample which were found to be close to the effective Eddington limit (NGC 454, 2MASX J03565655-4041453 and XSS J05054-2348), using newly obtained XMM-Newton data. We use the X-ray data to better constrain the absorbing column density, and supplement them with XMM Optical Monitor data, infrared Spitzer and Herschel data were available to construct a broad-band spectral energy distribution to estimate refined bolometric luminosities and Eddington ratios for these three objects. The new XMM-Newton observations show all three objects moving away from the region expected for short-lived absorption in the NH-λEdd plane into the `long-lived absorption' region. We find our conclusions robust to different methods for estimating the bolometric luminosity and Eddington ratio. Interestingly, 2MASX J03565655-4041453 and XSS J05054-2348 now exhibit complex X-ray spectra, at variance with previous analyses of their Swift/X-Ray Telescope data. We find evidence for absorption variability in NGC 454 and 2MASX J03565655-4041453, perhaps implying that although the radiation pressure from the central engine is insufficient to cause clearly detectable outflows, it may cause absorption variations over longer time-scales. However, more robust black hole mass estimates would improve the accuracy of the Eddington ratio estimates for these objects.

  7. Neutron-Proton Pairing Effect on One-Proton and Two-Proton Separation Energies in Rare-Earth Proton-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Hammache, F.; Allal, N. H.; Fellah, M.

    2012-12-01

    The one-proton and two-proton separation energies are studied for "ordinary" and rare-earth proton-rich nuclei by including the isovector neutron-proton (np) pairing correlations using the BCS approximation. Even-even as well as odd nuclei are considered. In the latter case, the wave function is defined using the blocked-level technique. The single-particle energies used are those of a deformed Woods-Saxon mean field. It is shown that the np isovector pairing effects on the one-proton and two-proton separation energies are non-negligible. However, the only isovector BCS approximation seems to be inadequate for a good description of these quantities when including the np pairing effects: either a particle-number projection or the inclusion of the isoscalar pairing effect seems to be necessary. Another possible improvement would be a more realistic choice of the pairing strengths.

  8. Conversion electron spectroscopy at the FMA focal plane: Decay studies of proton-rich N {approximately} 82 nuclei

    SciTech Connect

    Nisius, D.; Janssens, R.V.F.; Ahmad, I.

    1995-08-01

    The FMA has proven to be an ideal instrument for the detailed study of the decay of microsecond isomers behind the focal plane following mass selection. In reactions leading to the population of nuclei with isomeric lifetimes longer than their flight time through the device, decay gamma rays and conversion electrons can be detected in an environment free from the backgrounds of prompt radiation and delta electrons. This was a very successful technique to study proton (h{sub 11/2}){sup n} seniority isomers in nuclei with Z > 64 and N {approximately} 82. Since isomeric decay gamma rays are emitted isotropically, conversion electrons are essential for the assignment of multipolarities in these nuclei. Furthermore, the low-energy transitions that depopulate isomeric states are typically highly converted and can escape gamma-ray detection, but they can be identified by their conversion electrons.

  9. Observation of new K isomers among neutron-rich rare earth nuclei produced by in-flight fission of 345 MeV/nucleon 238U

    NASA Astrophysics Data System (ADS)

    Kameda, Daisuke; Kubo, Toshiyuki; BigRIPS new isotope Collaboration

    2014-09-01

    We have performed search for new K isomers for a wide range of neutron-rich rare earth nuclei using the BigRIPS separator at RIKEN RIBF. The rare earth nuclei were produced by in-flight fission of a 238U beam at 345 MeV/nucleon, and isomeric gamma rays were detected using four clover-type germanium detectors. As a result, we have observed a total of 25 new microsecond isomers: 158 m , 159 m , 160 mNd, 158 m , 159 m , 161 mPm, 160 m , 161 m , 162 mSm, 163 m , 164 mEu, 162 m , 164 m , 165 m , 166 mGd, 164 m , 165 m , 166 m , 167 m , 168 mTb, 167 m , 168 m , 169 m , 170 mDy, and 171mHo, and obtained a wealth of spectroscopic information on these nuclei. The nuclei in this region are predicted to be well deformed with a prolate shape, and Kisomers are expected to appear due to the K hindrance. In the present measurement, as anticipated, many of the observed new isomers have been interpreted as a K isomer, because we could identify some gamma rays which belong to the grand-state rotational band being fed by isomeric transitions. The systematics of known K isomers, such as those in neighboring higher- Zisotones, also help and support the interpretation of isomerism. Here we will report on the details of the experimental results and discuss the possible configurations of deformed orbits for the observed new K isomers.

  10. Description of nuclear octupole and quadrupole deformation close to axial symmetry: Octupole vibrations in the X(5) nuclei {sup 150}Nd and {sup 152}Sm

    SciTech Connect

    Bizzeti, P. G.; Bizzeti-Sona, A. M.

    2010-03-15

    The model, introduced in a previous paper, for the description of the octupole and quadrupole degrees of freedom in conditions close to the axial symmetry is used to describe the negative-parity band based on the first octupole vibrational state in nuclei close to the critical point of the U(5)-to-SU(3) phase transition. The situation of {sup 150}Nd and {sup 152}Sm is discussed in detail. The positive-parity levels of these nuclei, and also the in-band E2 transitions, are reasonably accounted for by the X(5) model. With simple assumptions on the nature of the octupole vibrations, it is also possible to describe the negative-parity sector with comparable accuracy without changing the description of the positive-parity part.

  11. Neutron Transfer Reactions on Neutron-Rich N=50 and N=82 Nuclei Near the r-Process Path

    SciTech Connect

    Cizewski, J. A.; Jones, K. L.; Kozub, R. L.; Pain, S. D.; Thomas, J. S.; Arbanas, Goran; Adekola, Aderemi S; Bardayan, Daniel W; Blackmon, Jeff C; Chae, K. Y.; Chipps, K.; Dean, David Jarvis; Erikson, Luke; Gaddis, A. L.; Harlin, Christopher W; Hatarik, Robert; Howard, Joshua A; Johnson, Micah; Kapler, R.; Krolas, W.; Liang, J Felix; Livesay, Jake; Ma, Zhanwen; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D; O'Malley, Patrick; Paulauskas, Stanley V; Shapira, Dan; ShrinerJr., J. F.; Sissom, D. J.; Smith, Michael Scott; Swan, T. P.; Wilson, Gemma L

    2009-01-01

    Neutron transfer (d,p) reaction studies on the N = 50 isotones, 82Ge and 84Se, and A{approx}130 nuclei, 130,132Sn and 134Te, have been measured. Direct neutron capture cross sections for 82Ge and 84Se (n,?) have been calculated and are combined with Hauser-Feshbach expectations to estimate total (n,?) cross sections. The A{approx}130 studies used an early implementation of the ORRUBA array of position-sensitive silicon strip detectors for reaction proton measurements. Preliminary excitation energy and angular distribution results from the A{approx}130 measurements are reported.

  12. Study of cluster structures in 10Be and 16C neutron-rich nuclei via break-up reactions

    NASA Astrophysics Data System (ADS)

    Dell'Aquila, D.; Acosta, L.; Amorini, F.; Andolina, R.; Auditore, L.; Berceanu, I.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gnoffo, B.; Grzeszczuk, A.; Lanzalone, G.; Lombardo, I.; Martorana, N.; Minniti, T.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Pop, A.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2016-05-01

    Projectile break-up reactions induced on polyethylene (CH2) target are used in order to study the spectroscopy of 10Be and 16C nuclei. For the present experiment we used 10Be and 16C beams delivered by the FRIBs facility at INFN-LNS, and the CHIMERA 4π multi-detector. 10Be and 16C structures are studied via a relative energy analysis of break-up fragments. The 4He+6He break-up channel allowed us to study the spectroscopy of 10Be; in particular we find evidence of a new state in 10Be at 13.5 MeV excitation energy. The 16C nucleus is studied via 6He-10Be correlation; we find the fingerprint of a possible state at about 20.6 MeV

  13. Neutron Transfer Reactions on Neutron-Rich N = 50 and N = 82 Nuclei Near the r-Process Path

    SciTech Connect

    Cizewski, J. A.; Hatarik, R.; Jones, K. L.; Kozub, R. L.; Paulauskas, S. V.; Shriner, J. F.; Sissom, D. J.; Pain, S. D.; Thomas, J. S.; Swan, T.; Wilson, G. L.; Arbanas, G.; Bardayan, D. W.; Blackmon, J. C.; Dean, D.; Liang, F.; Shapira, D.; Smith, M. S.; Adekola, A.; Chae, K. Y.

    2009-01-28

    Neutron transfer (d,p) reaction studies on the N = 50 isotones, {sup 82}Ge and {sup 84}Se, and A{approx_equal}130 nuclei, {sup 130,132}Sn and {sup 134}Te, have been measured. Direct neutron capture cross sections for {sup 82}Ge and {sup 84}Se (n,{gamma}) have been calculated and are combined with Hauser-Feshbach expectations to estimate total (n,{gamma}) cross sections. The A{approx_equal}130 studies used an early implementation of the ORRUBA array of position-sensitive silicon strip detectors for reaction proton measurements. Preliminary excitation energy and angular distribution results from the A{approx_equal}130 measurements are reported.

  14. ZIRCONIUM—HAFNIUM ISOTOPE EVIDENCE FROM METEORITES FOR THE DECOUPLED SYNTHESIS OF LIGHT AND HEAVY NEUTRON-RICH NUCLEI

    SciTech Connect

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-10

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope {sup 96}Zr (≤1ε in {sup 96}Zr/{sup 90}Zr) for bulk chondrites and CAIs (∼2ε). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the {sup 96}Zr isotope variations are of nucleosynthetic origin. The {sup 96}Zr enrichments are coupled with {sup 50}Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A ≤ 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. {sup 96}Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M{sub ☉}) SNII.

  15. Zirconium—Hafnium Isotope Evidence from Meteorites for the Decoupled Synthesis of Light and Heavy Neutron-rich Nuclei

    NASA Astrophysics Data System (ADS)

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-01

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope 96Zr (<=1ɛ in 96Zr/90Zr) for bulk chondrites and CAIs (~2ɛ). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the 96Zr isotope variations are of nucleosynthetic origin. The 96Zr enrichments are coupled with 50Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A <= 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. 96Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M ⊙) SNII.

  16. Beta Decay of the Proton-Rich Nuclei 102Sn and 104Sn

    SciTech Connect

    Karny, M.; Batist, L.; Banu, A.; Becker, F.; Blazhev, A.; Brown, B. A.; Bruchle, W.; Doring, J.; Faestermann, T.; Gorska, M.; Grawe, H.; Janas, Z.; Jungclaus, A.; Kavatsyuk, M.; Kavatsyuk, O.; Kirchner, R.; La Commara, M.; Mandal, S.; Mazzocchi, C.; Miernik, K.; Mukha, I.; Muralithar, S.; Plettner, C.; Plochocki, A.; Roeckl, E.; Romoli, M.; Rykaczewski, Krzysztof Piotr; Schadel, M.; Schmidt, K.; Schwengner, R.; Zylicz, J.

    2006-01-01

    The {beta} decays of {sup 102}Sn and {sup 104}Sn were studied by using high-resolution germanium detectors as well as a Total Absorption Spectrometer (TAS). For {sup 104}Sn, with three new {beta}-delayed {gamma}-rays identified, the total Gamow-Teller strength (BGT) value of 2.7(3) was obtained. For {sup 102}Sn, the {gamma}-{gamma} coincidence data were collected for the first time, allowing us to considerably extend the decay scheme. This scheme was used to unfold the TAS data and to deduce a BGT value of 4.2(8) for this decay. This result is compared to shell model predictions, yielding a hindrance factor of 3.6(7) in agreement with those obtained previously for {sup 98}Cd and {sup 100}In. Together with the latter two, {sup 102}Sn completes the triplet of Z {le} 50, N {ge} 50 nuclei with two proton holes, one proton hole and one neutron particle, and two neutron particles with respect to the doubly magic {sup 100}Sn core.

  17. Ultraviolet observations of close-binary and pulsating nuclei of planetary nebulae; Winds and shells around low-mass supergiants; The close-binary nucleus of the planetary nebula HFG-1; A search for binary nuclei of planetary nebulae; UV monitoring of irregularly variable planetary nuclei; and The pulsating nucleus of the planetary nebula Lo 4

    NASA Technical Reports Server (NTRS)

    Bond, Howard E.

    1992-01-01

    A brief summary of the research highlights is presented. The topics covered include the following: binary nuclei of planetary nebulae; other variable planetary nuclei; low-mass supergiants; and other IUE-related research.

  18. Distinction between elastic scattering of weakly bound proton- and neutron-rich nuclei: The case of 8B and 11Be

    NASA Astrophysics Data System (ADS)

    Yang, Y. Y.; Liu, X.; Pang, D. Y.

    2016-09-01

    Experimental data show that the elastic scattering cross sections of the neutron-rich nucleus 11Be are greatly reduced by the coupling effects from the breakup channels, while those of the proton-rich nucleus 8B are not. Such difference is found to persist in results of systematic calculations of 8B elastic scattering from 208Pb at 60 and 170.3 MeV and from 64Zn at 32 and 86 MeV, and 11Be elastic scattering from 208Pb at 55 and 143 MeV and from 64Zn at 29 and 66 MeV with the continuum-discretized coupled channel (CDCC) method. The Coulomb and centrifugal barriers experienced by the valence proton in the ground state of 8B, which do not exist for the valence neutron in the ground state of 11Be, are found to be the reason for such differences in the angular distributions of elastic scattering cross sections of these two weakly bound nuclei.

  19. Delayed triggering of radio Active Galactic Nuclei in gas-rich minor mergers in the local Universe

    NASA Astrophysics Data System (ADS)

    Shabala, S. S.; Deller, A.; Kaviraj, S.; Middelberg, E.; Turner, R. J.; Ting, Y. S.; Allison, J. R.; Davis, T. A.

    2016-10-01

    We examine the processes triggering star formation and Active Galactic Nucleus (AGN) activity in a sample of 25 low redshift (z < 0.13) gas-rich galaxy mergers observed at milli-arcsecond resolution with Very Long Baseline Interferometry as part of the mJy Imaging VLBA Exploration at 20cm (mJIVE-20) survey. The high (>107 K) brightness temperature required for an mJIVE-20 detection allows us to unambiguously identify the radio AGN in our sample. We find three such objects. Our VLBI AGN identifications are classified as Seyferts or LINERs in narrow line optical diagnostic plots; mid-infrared colours of our targets and the comparison of Hα star formation rates with integrated radio luminosity are also consistent with the VLBI identifications. We reconstruct star formation histories in our galaxies using optical and UV photometry, and find that these radio AGN are not triggered promptly in the merger process, consistent with previous findings for non-VLBI samples of radio AGN. This delay can significantly limit the efficiency of feedback by radio AGN triggered in galaxy mergers. We find that radio AGN hosts have lower star formation rates than non-AGN radio-selected galaxies at the same starburst age. Conventional and VLBI radio imaging shows these AGN to be compact on arcsecond scales. Our modeling suggests that the actual sizes of AGN-inflated radio lobes may be much larger than this, but these are too faint to be detected in existing observations. Deep radio imaging is required to map out the true extent of the AGN, and to determine whether the low star formation rates in radio AGN hosts are a result of the special conditions required for radio jet triggering, or the effect of AGN feedback.

  20. Production cross sections from 82Se fragmentation as indications of shell effects in neutron-rich isotopes close to the drip-line

    NASA Astrophysics Data System (ADS)

    Tarasov, O. B.; Portillo, M.; Morrissey, D. J.; Amthor, A. M.; Bandura, L.; Baumann, T.; Bazin, D.; Berryman, J. S.; Brown, B. A.; Chubarian, G.; Fukuda, N.; Gade, A.; Ginter, T. N.; Hausmann, M.; Inabe, N.; Kubo, T.; Pereira, J.; Sherrill, B. M.; Stolz, A.; Sumithrarachichi, C.; Thoennessen, M.; Weisshaar, D.

    2013-05-01

    Production cross sections for neutron-rich nuclei from the fragmentation of a 82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions of 126 neutron-rich isotopes of elements 11≤Z≤32 were scanned using an experimental approach of varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei including several isotopes first observed in this work. These are the most neutron-rich nuclides of the elements 22≤Z≤25 (64Ti, 67V, 69Cr, and 72Mn). One event was registered consistent with 70Cr and another one with 75Fe. The production cross sections are correlated with Qg systematics to reveal trends in the data. The results presented here confirm our previous results from a similar measurement using a 76Ge beam and can be explained with a shell model that predicts a subshell closure at N=34 around Z=20. This is demonstrated by systematic trends and calculations with the abrasion-ablation model that are sensitive to separation energies.

  1. The new neutron rich nuclei

    SciTech Connect

    Gridnev, K. A.; Gridnev, D. K.; Tarasov, V. N.; Tarasov, D. V.; Viñas, X.; Greiner, W.

    2014-07-23

    Using HF+BCS method with Skyrme forces we analyze the neutron drip line. It is shown that around magic and new magic numbers the drip line may form stability peninsulas. It is shown that the location of these peninsulas does not depend on the choice of Skyrme forces. It is found that the size of the peninsulas is sensitive to the choice of Skyrme forces and the most extended peninsulas appear with the SkI2 set.

  2. Introducing the fission-fusion reaction process: using a laser-accelerated Th beam to produce neutron-rich nuclei towards the N=126 waiting point of the r-process

    NASA Astrophysics Data System (ADS)

    Habs, D.; Thirolf, P. G.; Gross, M.; Allinger, K.; Bin, J.; Henig, A.; Kiefer, D.; Ma, W.; Schreiber, J.

    2011-05-01

    We propose to produce neutron-rich nuclei in the range of the astrophysical r-process (the rapid neutron-capture process) around the waiting point N=126 (Kratz et al. in Prog. Part. Nucl. Phys. 59:147, 2007; Arnould et al. in Phys. Rep. 450:97, 2007; Panov and Janka in Astron. Astrophys. 494:829, 2009) by fissioning a dense laser-accelerated thorium ion bunch in a thorium target (covered by a polyethylene layer, CH2), where the light fission fragments of the beam fuse with the light fission fragments of the target. Using the `hole-boring' (HB) mode of laser radiation pressure acceleration (RPA) (Robinson et al. in Plasma Phys. Control. Fusion 51:024004, 2009; Henig et al. in Phys. Rev. Lett. 103:245003, 2009; Tajima et al. in Rev. Accel. Sci. Technol. 2:221, 2009) using a high-intensity, short pulse laser, bunches of 232Th with solid-state density can be generated very efficiently from a Th layer (ca. 560 nm thick), placed beneath a deuterated polyethylene foil (CD2 with ca. 520 nm), both forming the production target. Th ions laser-accelerated to about 7 MeV/u will pass through a thin CH2 layer placed in front of a thicker second Th foil (both forming the reaction target) closely behind the production target and disintegrate into light and heavy fission fragments. In addition, light ions (d,C) from the CD2 production target will be accelerated as well to about 7 MeV/u, also inducing the fission process of 232Th in the second Th layer. The laser-accelerated ion bunches with solid-state density, which are about 1014 times more dense than classically accelerated ion bunches, allow for a high probability that generated fission products can fuse again when the fragments from the thorium beam strike the Th layer of the reaction target. In contrast to classical radioactive beam facilities, where intense but low-density radioactive beams of one ion species are merged with stable targets, the novel fission-fusion process draws on the fusion between neutron-rich, short

  3. In-beam {gamma}-ray study of the neutron-rich nuclei {sup 240}U, {sup 246}Pu, and {sup 250}Cm produced by the ({sup 18}O, {sup 16}O) reaction

    SciTech Connect

    Ishii, T. Shigematsu, S.; Makii, H.; Asai, M.; Tsukada, K.; Toyoshima, A.; Matsuda, M.; Makishima, A.; Shizuma, T.; Kaneko, J.; Hossain, I.; Toume, H.; Ohara, M.; Ichikawa, S.; Kohno, T.; Ogawa, M.

    2007-08-15

    We have measured deexcitation {gamma} rays in the neutron-rich nuclei of {sup 240}U, {sup 246}Pu, and {sup 250}Cm produced by the ({sup 18}O, {sup 16}O) two-neutron transfer reactions, in coincidence with the {sup 16}O particles using Si {delta}E-E detectors. The {gamma} rays in these nuclei were identified by selecting the kinetic energies of {sup 16}O particles, which correspond to the excitation energies in the residual nuclei below the neutron separation energies. The ground-state bands of {sup 240}U, {sup 246}Pu, and {sup 250}Cm were established up to 12{sup +} states and the K{sup {pi}} = 0{sup -} octupole band of {sup 240}U was established up to 9{sup -} states. The systematics of the moments of inertia of the ground-state bands for actinide nuclei shows that the deformed subshell closure at N = 152 is sustained for {sub 96}Cm isotopes and that it disappears for {sub 94}Pu isotopes.

  4. Fast convergence of learning requires plasticity between inferior olive and deep cerebellar nuclei in a manipulation task: a closed-loop robotic simulation

    PubMed Central

    Luque, Niceto R.; Garrido, Jesús A.; Carrillo, Richard R.; D'Angelo, Egidio; Ros, Eduardo

    2014-01-01

    The cerebellum is known to play a critical role in learning relevant patterns of activity for adaptive motor control, but the underlying network mechanisms are only partly understood. The classical long-term synaptic plasticity between parallel fibers (PFs) and Purkinje cells (PCs), which is driven by the inferior olive (IO), can only account for limited aspects of learning. Recently, the role of additional forms of plasticity in the granular layer, molecular layer and deep cerebellar nuclei (DCN) has been considered. In particular, learning at DCN synapses allows for generalization, but convergence to a stable state requires hundreds of repetitions. In this paper we have explored the putative role of the IO-DCN connection by endowing it with adaptable weights and exploring its implications in a closed-loop robotic manipulation task. Our results show that IO-DCN plasticity accelerates convergence of learning by up to two orders of magnitude without conflicting with the generalization properties conferred by DCN plasticity. Thus, this model suggests that multiple distributed learning mechanisms provide a key for explaining the complex properties of procedural learning and open up new experimental questions for synaptic plasticity in the cerebellar network. PMID:25177290

  5. Synthesis of superheavy nuclei: Obstacles and opportunities

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Greiner, Walter

    2015-01-01

    There are only 3 methods for the production of heavy and superheavy (SH) nuclei, namely, fusion reactions, a sequence of neutron capture and beta(-) decay and multinucleon transfer reactions. Low values of the fusion cross sections and very short half-lives of nuclei with Z<120 put obstacles in synthesis of new elements. At the same time, an important area of SH isotopes located between those produced in the cold and hot fusion reactions remains unstudied yet. This gap could be filled in fusion reactions of 48Ca with available lighter isotopes of Pu, Am, and Cm. New neutron-enriched isotopes of SH elements may be produced with the use of a 48Ca beam if a 250Cm target would be prepared. In this case we get a real chance to reach the island of stability owing to a possible beta(+) decay of 291114 and 287112 nuclei formed in this reaction with a cross section of about 0.8 pb. A macroscopic amount of the long-living SH nuclei located at the island of stability may be produced by using the pulsed nuclear reactors of the next generation only if the neutron fluence per pulse will be increased by about three orders of magnitude. Multinucleon transfer processes look quite promising for the production and study of neutron-rich heavy nuclei located in upper part of the nuclear map not reachable by other reaction mechanisms. Reactions with actinide beams and targets are of special interest for synthesis of new neutron-enriched transfermium nuclei and not-yet-known nuclei with closed neutron shell N=126 having the largest impact on the astrophysical r-process. The estimated cross sections for the production of these nuclei allows one to plan such experiments at currently available accelerators.

  6. Spectroscopy of neutron-rich {sup 168,170}Dy: Yrast band evolution close to the N{sub p}N{sub n} valence maximum

    SciTech Connect

    Soederstroem, P.-A.; Nyberg, J.; Regan, P. H.; Ashley, S. F.; Catford, W. N.; Gelletly, W.; Jones, G. A.; Liu, Z.; Pietri, S.; Podolyak, Zs.; Steer, S. J.; Thompson, N. J.; Williams, S. J.; Algora, A.; Angelis, G. de; Corradi, L.; Fioretto, E.; Gottardo, A.; Grodner, E.; He, C. Y.

    2010-03-15

    The yrast sequence of the neutron-rich dysprosium isotope {sup 168}Dy has been studied using multinucleon transfer reactions following collisions between a 460-MeV {sup 82}Se beam and an {sup 170}Er target. The reaction products were identified using the PRISMA magnetic spectrometer and the gamma rays detected using the CLARA HPGe-detector array. The 2{sup +} and 4{sup +} members of the previously measured ground-state rotational band of {sup 168}Dy have been confirmed and the yrast band extended up to 10{sup +}. A tentative candidate for the 4{sup +}->2{sup +} transition in {sup 170}Dy was also identified. The data on these nuclei and on the lighter even-even dysprosium isotopes are interpreted in terms of total Routhian surface calculations and the evolution of collectivity in the vicinity of the proton-neutron valence product maximum is discussed.

  7. β-Decay half-lives and nuclear structure of exotic proton-rich waiting point nuclei under rp-process conditions

    NASA Astrophysics Data System (ADS)

    Nabi, Jameel-Un; Böyükata, Mahmut

    2016-03-01

    We investigate even-even nuclei in the A ∼ 70 mass region within the framework of the proton-neutron quasi-particle random phase approximation (pn-QRPA) and the interacting boson model-1 (IBM-1). Our work includes calculation of the energy spectra and the potential energy surfaces V (β , γ) of Zn, Ge, Se, Kr and Sr nuclei with the same proton and neutron number, N = Z. The parametrization of the IBM-1 Hamiltonian was performed for the calculation of the energy levels in the ground state bands. Geometric shape of the nuclei was predicted by plotting the potential energy surfaces V (β , γ) obtained from the IBM-1 Hamiltonian in the classical limit. The pn-QRPA model was later used to compute half-lives of the neutron-deficient nuclei which were found to be in very good agreement with the measured ones. The pn-QRPA model was also used to calculate the Gamow-Teller strength distributions and was found to be in decent agreement with the measured data. We further calculate the electron capture and positron decay rates for these N = Z waiting point (WP) nuclei in the stellar environment employing the pn-QRPA model. For the rp-process conditions, our total weak rates are within a factor two compared with the Skyrme HF +BCS +QRPA calculation. All calculated electron capture rates are comparable to the competing positron decay rates under rp-process conditions. Our study confirms the finding that electron capture rates form an integral part of the weak rates under rp-process conditions and should not be neglected in the nuclear network calculations.

  8. {gamma}-ray spectroscopy of the neutron-rich nuclei {sup 89}Rb, {sup 92}Y, and {sup 93}Y with multinucleon transfer reactions

    SciTech Connect

    Bucurescu, D.; Ionescu-Bujor, M.; Iordachescu, A.; Mihai, C.; Suliman, G.; Rusu, C.; Marginean, N.; Ur, C. A.; Marginean, R.; De Angelis, G.; Corradi, L.; Vedova, F. Della; Fioretto, E.; Gadea, A.; Guiot, B.; Napoli, D.; Stefanini, A. M.; Valiente-Dobon, J. J.; Bazzacco, D.; Beghini, S.

    2007-12-15

    The positive-parity yrast states in the {sup 89}Rb, {sup 92}Y, and {sup 93}Y nuclei were studied using {gamma}-ray spectroscopy with heavy-ion induced reactions. In the multinucleon transfer reactions {sup 208}Pb+{sup 90}Zr (590 MeV) and {sup 238}U+{sup 82}Se (505 MeV), several {gamma}-ray transitions were identified in these nuclei by means of coincidences between recoiling ions identified with the PRISMA spectrometer and {gamma} rays detected with the CLARA {gamma}-ray array in thin target experiments. Level schemes were subsequently determined from triple-{gamma} coincidences recorded with the GASP array in a thick target experiment, in the reactions produced by a 470 MeV {sup 82}Se beam with a {sup 192}Os target. The observed level schemes are compared to shell-model calculations.

  9. Petrology and mineralogy of Type II, FeO-rich chondrules in Semarkona (LL3.0) - Origin by closed-system fractional crystallization, with evidence for supercooling

    NASA Technical Reports Server (NTRS)

    Jones, Rhian H.

    1990-01-01

    The petrology of type II porphyritic olivine chondrules in Semarkona (LL3.0) has been studied in detail. Olivines in these chondrules are euhedral, Fe-rich, and are strongly zoned from cores to rims of grains in FeO (Fa10-30), Cr2O3 (0.2-0.6 wt pct), MnO (0.2-0.7 wt pct), and CaO (0.1-0.4 wt pct). Interstitial mesostasis is rich in Si, Al, and Ca and is glassy with abundant microcrystallites. Minor minerals include troilite, Fe,Ni metal, and chromite. Some olivine grains contain euhedral, fayalite-rich cores that are probably produced during initial supercooling of the chondrule melt. Rare relict grains of forsteritic olivine have compositions very similar to olivines in type IA chondrules in Semarkona and may result from disaggregation of such chondrules. Apart from these relics, all properties of type II chondrules can be described by closed-system fractional crystallization of droplets which were essentially entirely molten. Type IA chondrules may have formed from type II chondrules by loss of Fe and volatiles. Alternatively, the two chondrule types may have formed in regions of considerable diversity in the solar nebula from precursor materials with different Fe/Mg ratios.

  10. Identification of highly deformed even-even nuclei in the neutron- and proton-rich regions of the nuclear chart from the B(E2)↑ and E2 predictions in the generalized differential equation model

    NASA Astrophysics Data System (ADS)

    Nayak, R. C.; Pattnaik, S.

    2015-11-01

    We identify here the possible occurrence of large deformations in the neutron- and proton-rich (n-rich and p-rich) regions of the nuclear chart from extensive predictions of the values of the reduced quadrupole transition probability B(E2)↑ for the transition from the ground state to the first 2+ state and the corresponding excitation energy E2 of even-even nuclei in the recently developed generalized differential equation (GDE) model exclusively meant for these physical quantities. This is made possible from our analysis of the predicted values of these two physical quantities and the corresponding deformation parameters derived from them such as the quadrupole deformation β2, the ratio of β2 to the Weisskopf single-particle β2(sp) and the intrinsic electric quadrupole moment Q0, calculated for a large number of both known as well as hitherto unknown even-even isotopes of oxygen to fermium (0 to FM; Z = 8-100). Our critical analysis of the resulting data convincingly support possible existence of large collectivity for the nuclides 30,32Ne,34Mg, 60Ti, 42,62,64Cr,50,68Fe, 52,72Ni, 72,70,96Kr,74,76Sr,78,80,106,108Zr, 82,84,110,112Mo, 140Te,144Xe, 148Ba,122Ce, 128,156Nd,130,132,158,160Sm and 138,162,164,166Gd, whose values of β2 are found to exceed 0.3 and even 0.4 in some cases. Our findings of large deformations in the exotic n-rich regions support the existence of another “island of inversion” in the heavy-mass region possibly caused by breaking of the N = 70 subshell closure.

  11. Physics of Unstable Nuclei

    NASA Astrophysics Data System (ADS)

    Khoa, Dao Tien; Egelhof, Peter; Gales, Sydney; Giai, Nguyen Van; Motobayashi, Tohru

    2008-04-01

    Studies at the RIKEN RI beam factory / T. Motobayashi -- Dilute nuclear states / M. Freer -- Studies of exotic systems using transfer reactions at GANIL / D. Beaumel et al. -- First results from the Magnex large-acceptance spectrometer / A. Cunsolo et al. -- The ICHOR project and spin-isospin physics with unstable beams / H. Sakai -- Structure and low-lying states of the [symbol]He exotic nucleus via direct reactions on proton / V. Lapoux et al. -- Shell gap below [symbol]Sn based on the excited states in [symbol]Cd and [symbol]In / M. Górska -- Heavy neutron-rich nuclei produced in the fragmentation of a [symbol]Pb beam / Zs. Podolyák et al. -- Breakup and incomplete fusion in reactions of weakly-bound nuclei / D.J. Hinde et al. -- Excited states of [symbol]B and [symbol]He and their cluster aspect / Y. Kanada-En'yo et al. -- Nuclear reactions with weakly-bound systems: the treatment of the continuum / C. H. Dasso, A. Vitturi -- Dynamic evolution of three-body decaying resonances / A. S. Jensen et al. -- Prerainbow oscillations in [symbol]He scattering from the Hoyle state of [symbol]C and alpha particle condensation / S. Ohkubo, Y. Hirabayashi -- Angular dispersion behavior in heavy ion elastic scattering / Q. Wang et al. -- Microscopic optical potential in relativistic approach / Z.Yu. Ma et al. -- Exotic nuclei studied in direct reactions at low momentum transfer - recent results and future perspectives at fair / P. Egelhof -- Isotopic temperatures and symmetry energy in spectator fragmentation / M. De Napoli et al. -- Multi-channel algebraic scattering theory and the structure of exotic compound nuclei / K. Amos et al. -- Results for the first feasibility study for the EXL project at the experimental storage ring at GSI / N. Kalantar-Nayestanaki et al. -- Coulomb excitation of ISOLDE neutron-rich beams along the Z = 28 chain / P. Van Duppen -- The gamma decay of the pygmy resonance far from stability and the GDR at finite temperature / G. Benzoni et al

  12. Shell closures, loosely bound structures, and halos in exotic nuclei

    SciTech Connect

    Saxena, G.; Singh, D.

    2013-04-15

    Inspired by the recent experiments indicating doubly magic nuclei that lie near the drip-line and encouraged by the success of our relativistic mean-field (RMF) plus state-dependent BCS approach to the description of the ground-state properties of drip-line nuclei, we develop this approach further, across the entire periodic table, to explore magic nuclei, loosely bound structures, and halo formation in exotic nuclei. In our RMF+BCS approach, the single-particle continuum corresponding to the RMF is replaced by a set of discrete positive-energy states for the calculations of pairing energy. Detailed analysis of the single-particle spectrum, pairing energies, and densities of the nuclei predict the unusual proton shell closures at proton numbers Z = 6, 14, 16, 34, and unusual neutron shell closures at neutron numbers N = 6, 14, 16, 34, 40, 70, 112. Further, in several nuclei like the neutron-rich isotopes of Ca, Zr, Mo, etc., the gradual filling of lowlying single-particle resonant state together with weakly bound single-particle states lying close to the continuum threshold helps accommodate more neutrons but with an extremely small increase in the binding energy. This gives rise to the occurrence of loosely bound systems of neutron-rich nuclei with a large neutron-to-proton ratio. In general, the halo-like formation, irrespective of the existence of any resonant state, is seen to be due to the large spatial extension of the wave functions for the weakly bound single-particle states with low orbital angular momentum having very small or no centrifugal barriers.

  13. Improvements to the on-line mass separator, RAMA, and the beta-delayed charged-particle emission of proton-rich sd shell nuclei

    SciTech Connect

    Ognibene, T.J.

    1996-03-01

    To overcome the extreme difficulties encountered in the experimental decay studies of proton drip line nuclei, several techniques have been utilized, including a helium-jet transport system, particle identification detectors and mass separation. Improvements to the ion source/extraction region of the He-jet coupled on-line Recoil Atom Mass Analyzer (RAMA) and its target/ion source coupling resulted in significant increases in RAMA efficiencies and its mass resolution, as well as reductions in the overall transit time. At the 88-Inch Cyclotron at LBNL, the decays of {sup 31}Cl, {sup 27}P and {sup 28}P, with half-lives of 150 msec, 260 msec and 270.3 msec, respectively, were examined using a he-jet and low-energy gas {Delta}E-gas {Delta}E-silicon E detector telescopes. Total beta-delayed proton branches of 0.3% and 0.07% in {sup 31}Cl and {sub 27}P, respectively, were estimated. Several proton peaks that had been previously assigned to the decay of {sup 31}Cl were shown to be from the decay of {sup 25}Si. In {sup 27}P, two proton groups at 459 {+-} 14 keV and 610 {+-} 11 keV, with intensities of 7 {+-} 3% and 92 {+-} 4% relative to the main (100%) group were discovered. The Gamow-Teller component of the preceding beta-decay of each observed proton transition was compared to results from shell model calculations. Finally, a new proton transition was identified, following the {beta}-decay of {sup 28}P, at 1,444 {+-} 12 keV with a 1.7 {+-} 0.5% relative intensity to the 100% group. Using similar low-energy detector telescopes and the mass separator TISOL at TRIUMF, the 109 msec and 173 msec activities, {sup 17}Ne and {sup 33}Ar, were studied. A new proton group with energy 729 {+-} 15 keV was observed following the beta-decay of {sup 17}Ne. Several discrepancies between earlier works as to the energies, intensities and assignments of several proton transitions from {sup 17}Ne and {sup 33}Ar were resolved.

  14. Systematic study of favored α -decay half-lives of closed shell odd-A and doubly-odd nuclei related to ground and isomeric states

    NASA Astrophysics Data System (ADS)

    Sun, Xiao-Dong; Guo, Ping; Li, Xiao-Hua

    2016-08-01

    In this work, we systematically investigate the favored α -decay half-lives and α preformation probabilities of both odd-A and doubly-odd nuclei related to ground and isomeric states around the doubly magic cores at Z =82 , N =82 and at Z =82 , N =126 , respectively, within a two-potential approach from the view of the valence nucleon (or hole). The results show that the α preformation probability is linearly related to NpNn or NpNnI , where Np, Nn, and I are the number of valence protons (or holes), the number of valence neutrons (or holes), and the isospin of the parent nucleus, respectively. Fitting the α preformation probabilities data extracted from the differences between experimental data and calculated half-lives without a shell correction, we give two analytic formulas of the α preformation probabilities and the values of corresponding parameters. Using those formulas and the parameters, we calculate the α -decay half-lives for those nuclei. The calculated results can well reproduce the experimental data.

  15. β -Decay Half-Lives of 110 Neutron-Rich Nuclei across the N =82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process

    NASA Astrophysics Data System (ADS)

    Lorusso, G.; Nishimura, S.; Xu, Z. Y.; Jungclaus, A.; Shimizu, Y.; Simpson, G. S.; Söderström, P.-A.; Watanabe, H.; Browne, F.; Doornenbal, P.; Gey, G.; Jung, H. S.; Meyer, B.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Baba, H.; Benzoni, G.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Inabe, N.; Isobe, T.; Kajino, T.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lane, G. J.; Li, Z.; Montaner-Pizá, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Sakurai, H.; Schaffner, H.; Schury, P.; Shibagaki, S.; Steiger, K.; Suzuki, H.; Takeda, H.; Wendt, A.; Yagi, A.; Yoshinaga, K.

    2015-05-01

    The β -decay half-lives of 110 neutron-rich isotopes of the elements from Rb 37 to Sn 50 were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r -process calculations and reinforce the notion that the second (A ≈130 ) and the rare-earth-element (A ≈160 ) abundance peaks may result from the freeze-out of an (n ,γ )⇄(γ ,n ) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r -process events.

  16. Critical-point nuclei

    SciTech Connect

    Clark, R.M.

    2004-10-01

    It has been suggested that a change of nuclear shape may be described in terms of a phase transition and that specific nuclei may lie close to the critical point of the transition. Analytical descriptions of such critical-point nuclei have been introduced recently and they are described briefly. The results of extensive searches for possible examples of critical-point behavior are presented. Alternative pictures, such as describing bands in the candidate nuclei using simple {Delta}K = 0 and {Delta}K = 2 rotational-coupling models, are discussed, and the limitations of the different approaches highlighted. A possible critical-point description of the transition from a vibrational to rotational pairing phase is suggested.

  17. Nucleon-nucleon momentum-correlation function as a probe of the density distribution of valence neutrons in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Cao, X. G.; Cai, X. Z.; Ma, Y. G.; Fang, D. Q.; Zhang, G. Q.; Guo, W.; Chen, J. G.; Wang, J. S.

    2012-10-01

    Proton-neutron, neutron-neutron, and proton-proton momentum-correlation functions (Cpn,Cnn, and Cpp) are systematically investigated for 15C and other C-isotope-induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum-molecular-dynamics model complemented by the correlation after burner (crab) computation code. 15C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron-shell nucleus 14C. To study density dependence of the correlation function by removing the isospin effect, the initialized 15C projectiles are sampled from two kinds of density distribution from the relativistic mean-field (RMF) model in which the valence neutron of 15C is populated in both 1d5/2 and 2s1/2 states, respectively. The results show that the density distributions of the valence neutron significantly influence the nucleon-nucleon momentum-correlation function at large impact parameters and high incident energies. The extended density distribution of the valence neutron largely weakens the strength of the correlation function. The size of the emission source is extracted by fitting the correlation function by using the Gaussian source method. The emission source size as well as the size of the final-state phase space are larger for projectile samplings from more extended density distributions of the valence neutron, which corresponds to the 2s1/2 state in the RMF model. Therefore, the nucleon-nucleon momentum-correlation function can be considered as a potentially valuable tool to diagnose exotic nuclear structures, such as the skin and halo.

  18. Cosmogenic nuclei

    NASA Technical Reports Server (NTRS)

    Raisbeck, G. M.

    1986-01-01

    Cosmogenic nuclei, nuclides formed by nuclear interactions of galactic and solar cosmic rays with extraterrestrial or terrestrial matter are discussed. Long lived radioactive cosmogenic isotopes are focused upon. Their uses in dating, as tracers of the interactions of cosmic rays with matter, and in obtaining information on the variation of primary cosmic ray flux in the past are discussed.

  19. Are the nuclei beyond 132Sn very exotic?

    NASA Astrophysics Data System (ADS)

    Lozeva, R.; Naïdja, H.; Nowacki, F.; Odahara, A.; Moon, C.-B.; NP1112-RIBF87 Collaboration

    2016-06-01

    The term exotic nucleus is used for nuclei that have different from normal behavior. However, it turns out that the term normal is valid only for nuclei close to stability and more particularly for regions close to double-shell closures. As long as one drives away in the neutron-rich nuclei, especially at intermediate mass number, interplay between normal single-particle and many collective particle-hole excitations compete. In some cases with the addition of neutrons, these may turn to evolve as a skin, acting against the core nucleus that may also influence its shell evolution. Knowledge of these nuclear ingredients is especially interesting beyond the doubly-magic 132Sn, however a little is known on how the excitations modes develop with the addition of both protons and neutrons. Especially for the Sb nuclei, where one gradually increases these valence particles, the orbital evolution and its impact on exoticness is very intriguing. Experimental studies were conducted on several such isotopes using isomer and, β-decay spectroscopy at RIBF within EURICA. In particular, new data on 140Sb and 136Sb are examined and investigated in the framework of shell model calculations.

  20. Evidence for {open_quotes}magnetic rotation{close_quotes} in nuclei: New results on the M1-bands of {sup 198,199}Pb

    SciTech Connect

    Clark, R.M.

    1996-12-31

    Lifetimes of states in four of the M1-bands in {sup 198,199}Pb have been determined through a Doppler Shift Attenuation Method measurement performed using the Gammasphere array. The deduced B(M1) values, which are a sensitive probe of the underlying mechanism for generating these sequences, show remarkable agreement with Tilted Axis Cranking (TAC) calculations. Evidence is also presented for the possible termination of the bands. The results represent clear evidence for a new concept in nuclear excitations: {open_quote}magnetic rotation{close_quote}.

  1. The Growth of Melt Inclusion- and Water-Rich Zones in Clinopyroxene Phenocrysts of the Powai Ankaramite Flow, Deccan Traps, India: Rapid Closed System Oscillatory Mineral Growth

    NASA Astrophysics Data System (ADS)

    Seaman, S. J.

    2015-12-01

    Water concentrations were measured and mapped using FTIR spectroscopy in clinopyroxene phenocrysts of the Powai ankaramite flow, located near Mumbai, west of the Western Ghats escarpment of the Deccan province, India. Samples were provided by Dr. Hetu Sheth of the Indian Institute of Technology, Mumbai. Chatterjee and Sheth (2015) showed that phenocrysts in the flow were part of a cumulate layer intruded by high-temperature basaltic melt at ~ 6 kb and ~1230oC. Cpx phenocrysts are euhedral and have concentric bands (100 to 200 microns thick) of fine (10-20 micron diameter) melt inclusions. Cpx bands that host melt inclusions have higher concentrations of water than inclusion-free bands. Water concentrations of cpx and ol were used to calculate water concentrations in the melt from which the crystals formed. Water concentrations in the parent magma were between 4.35 and 8.26 wt. % based on water concentrations in cpx, and between 8.24 and 9.41 wt. % based on those in ol. Both Mg and Fe are relatively depleted in the water- and melt inclusion-rich zones in cpx, and Ca is enriched in these zones. We suggest that oscillatory zoning in cpx is a result of repeated growth of cpx in water-richer and water-poorer boundary layers in which water lowered melt viscosity and enhanced diffusion and crystal growth rates. Water-enhanced growth rates may have resulted in preferential capture of melt inclusions preserved in water-rich cpx zones. Mg was preferentially incorporated into the cpx, causing Ca and water to build up in the boundary layer, and Mg and Fe to become relatively depleted in the boundary layer, as discussed for oscillatorially-zoned minerals by Wang and Merino (1993). Application of the equations for growth of oscillatory zones in crystals given by Wang and Merino (1993) to the growth of cpx crystals in the Powai ankaramite indicate that crystal growth occurred relatively quickly, on the order of days, although the width of the boundary zone, which is uncertain

  2. Three-cluster model for the α-accompanied fission of californium nuclei

    NASA Astrophysics Data System (ADS)

    Manimaran, K.; Balasubramaniam, M.

    2009-02-01

    A three-cluster model is proposed to explain the particle-accompanied binary fission of radioactive nuclei. The model is developed as an extension of the preformed cluster model of Gupta and collaborators. The advantage of this model is that, for a fixed third fragment, we can calculate the fragmentation potential minimized in charge coordinate. For our study we chose the various neutron-deficient to neutron-rich californium nuclei, whose analysis reveals that the closed-shell effect of any one of the fragments in ternary fragmentation presents itself as the most favorable configuration to be observed. As one goes from a neutron-deficient to a neutron-rich californium isotope, the role of the neutron closed shell associated with any one of the preferred fragments changes to that of the proton closed shell, and for very neutron rich isotopes of californium the presence of a double closed shell nucleus enhances the decay probability. The quadrupole deformation of the light fragment (A2) associated with the preferred configuration in the symmetric mass region also has a transition from positive to negative deformation as one goes from neutron-deficient to neutron-rich californium isotopes. The calculated relative yields of different fragmentation channels are compared with the available experimental yields for Cf252.

  3. Three-cluster model for the {alpha}-accompanied fission of californium nuclei

    SciTech Connect

    Manimaran, K.; Balasubramaniam, M.

    2009-02-15

    A three-cluster model is proposed to explain the particle-accompanied binary fission of radioactive nuclei. The model is developed as an extension of the preformed cluster model of Gupta and collaborators. The advantage of this model is that, for a fixed third fragment, we can calculate the fragmentation potential minimized in charge coordinate. For our study we chose the various neutron-deficient to neutron-rich californium nuclei, whose analysis reveals that the closed-shell effect of any one of the fragments in ternary fragmentation presents itself as the most favorable configuration to be observed. As one goes from a neutron-deficient to a neutron-rich californium isotope, the role of the neutron closed shell associated with any one of the preferred fragments changes to that of the proton closed shell, and for very neutron rich isotopes of californium the presence of a double closed shell nucleus enhances the decay probability. The quadrupole deformation of the light fragment (A{sub 2}) associated with the preferred configuration in the symmetric mass region also has a transition from positive to negative deformation as one goes from neutron-deficient to neutron-rich californium isotopes. The calculated relative yields of different fragmentation channels are compared with the available experimental yields for {sup 252}Cf.

  4. The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf

    NASA Astrophysics Data System (ADS)

    Hirano, Teruyuki; Fukui, Akihiko; Mann, Andrew W.; Sanchis-Ojeda, Roberto; Gaidos, Eric; Narita, Norio; Dai, Fei; Van Eylen, Vincent; Lee, Chien-Hsiu; Onozato, Hiroki; Ryu, Tsuguru; Kusakabe, Nobuhiko; Ito, Ayaka; Kuzuhara, Masayuki; Onitsuka, Masahiro; Tatsuuma, Misako; Nowak, Grzegorz; Pallè, Enric; Ribas, Ignasi; Tamura, Motohide; Yu, Liang

    2016-03-01

    We validate a {R}p=2.32+/- 0.24{R}\\oplus planet on a close-in orbit (P = 2.260455 ± 0.000041 days) around K2-28 (EPIC 206318379), a metal-rich M4-type dwarf in the Campaign 3 field of the K2 mission. Our follow-up observations included multi-band transit observations from the optical to the near-infrared, low-resolution spectroscopy, and high-resolution adaptive optics (AO) imaging. We perform a global fit to all of the observed transits using a Gaussian process-based method and show that the transit depths in all of the passbands adopted for the ground-based transit follow-ups ({r}2\\prime ,{z}s,2,J,H,{K}s) are within ˜2σ of the K2 value. Based on a model of the background stellar population and the absence of nearby sources in our AO imaging, we estimate the probability that a background eclipsing binary could cause a false positive to be <2 × 10-5. We also show that K2-28 cannot have a physically associated companion of stellar type later than M4, based on the measurement of almost identical transit depths in multiple passbands. There is a low probability for an M4 dwarf companion (≈ {0.072}-0.04+0.02), but even if this were the case, the size of K2-28b falls within the planetary regime. K2-28b has the same radius (within 1σ) and experiences irradiation from its host star similar to the well-studied GJ 1214b. Given the relative brightness of K2-28 in the near-infrared ({m}{Kep}=14.85 mag and mH = 11.03 mag) and relatively deep transit (0.6%-0.7%), a comparison between the atmospheric properties of these two planets with future observations would be especially interesting.

  5. Development of fluid veins during deformation of fluid-rich rocks close to the brittle-ductile transition: comparison between experimental and physical models.

    NASA Astrophysics Data System (ADS)

    Michel, Rabinowicz; Micha, Bystricky; Martin, Schmocker; Michael, Toplis; Alexis, Rigo; Hugo, Perfettini

    2010-05-01

    Laboratory experiments generally show that high temperature shear deformation of rocks rich in interstitial fluid leads to the development of long fluid veins parallel to R1 and R2 Riedel directions. This contradicts results of numerous mathematical models suggesting that deformation of a rock with a purely viscous solid rheology triggers fluid banding on planes orthogonal to the direction of maximal extension . High-temperature shear laboratory experiments on a sub-micron flint conducted in an internally heated Paterson apparatus with torsion capabilities (Schmocker et al. 2003; Schmocker 2002) reveal that: (i) flint deforms by grain boundary sliding and dissolution precipitation processes, leading to the development of fluid banding orthogonal to up to a strain of about 0.1-0.2; (ii) R1 and R2 fluid veins form beyond these strains, crossing the first generation of bands formed at low , (iii) during the whole deformation process, the strain rate remains perfectly uniform through the entire sample. In order to understand and rationalize these observations, one dimensional numerical modelling of fluid-rock separation during shear has been performed. The model assumes a constant strain rate and uses the interstitial fluid dependence of pressure-solution viscosity of quartz. When shearing is initiated, fluid and solid pressures are equal (pf = ps). Thereafter in zones of compaction, i.e. zones from which fluid is expelled, pf drops and the solid viscosity rises sharply. Although strain rate is uniform across the bulk sample, local stress sharply rises in the compaction bands but remains low in zones of fluid segregation. Indeed, the model shows that, in the zones of compaction, both the deviatoric stress and the excess pressure (pf - ps) have the same amplitude. Their value exceeds the bulk shear stress necessary to maintain the strain rate constant through the entire sample by a factor of about 5. To maintain a high strain rate during shear, laboratory experiments

  6. Constraining the astrophysical origin of the p-nuclei through nuclear physics and meteoritic data.

    PubMed

    Rauscher, T; Dauphas, N; Dillmann, I; Fröhlich, C; Fülöp, Zs; Gyürky, Gy

    2013-06-01

    A small number of naturally occurring, proton-rich nuclides (the p-nuclei) cannot be made in the s- and r-processes. Their origin is not well understood. Massive stars can produce p-nuclei through photodisintegration of pre-existing intermediate and heavy nuclei. This so-called γ-process requires high stellar plasma temperatures and occurs mainly in explosive O/Ne burning during a core-collapse supernova. Although the γ-process in massive stars has been successful in producing a large range of p-nuclei, significant deficiencies remain. An increasing number of processes and sites has been studied in recent years in search of viable alternatives replacing or supplementing the massive star models. A large number of unstable nuclei, however, with only theoretically predicted reaction rates are included in the reaction network and thus the nuclear input may also bear considerable uncertainties. The current status of astrophysical models, nuclear input and observational constraints is reviewed. After an overview of currently discussed models, the focus is on the possibility to better constrain those models through different means. Meteoritic data not only provide the actual isotopic abundances of the p-nuclei but can also put constraints on the possible contribution of proton-rich nucleosynthesis. The main part of the review focuses on the nuclear uncertainties involved in the determination of the astrophysical reaction rates required for the extended reaction networks used in nucleosynthesis studies. Experimental approaches are discussed together with their necessary connection to theory, which is especially pronounced for reactions with intermediate and heavy nuclei in explosive nuclear burning, even close to stability.

  7. Constraining the astrophysical origin of the p-nuclei through nuclear physics and meteoritic data.

    PubMed

    Rauscher, T; Dauphas, N; Dillmann, I; Fröhlich, C; Fülöp, Zs; Gyürky, Gy

    2013-06-01

    A small number of naturally occurring, proton-rich nuclides (the p-nuclei) cannot be made in the s- and r-processes. Their origin is not well understood. Massive stars can produce p-nuclei through photodisintegration of pre-existing intermediate and heavy nuclei. This so-called γ-process requires high stellar plasma temperatures and occurs mainly in explosive O/Ne burning during a core-collapse supernova. Although the γ-process in massive stars has been successful in producing a large range of p-nuclei, significant deficiencies remain. An increasing number of processes and sites has been studied in recent years in search of viable alternatives replacing or supplementing the massive star models. A large number of unstable nuclei, however, with only theoretically predicted reaction rates are included in the reaction network and thus the nuclear input may also bear considerable uncertainties. The current status of astrophysical models, nuclear input and observational constraints is reviewed. After an overview of currently discussed models, the focus is on the possibility to better constrain those models through different means. Meteoritic data not only provide the actual isotopic abundances of the p-nuclei but can also put constraints on the possible contribution of proton-rich nucleosynthesis. The main part of the review focuses on the nuclear uncertainties involved in the determination of the astrophysical reaction rates required for the extended reaction networks used in nucleosynthesis studies. Experimental approaches are discussed together with their necessary connection to theory, which is especially pronounced for reactions with intermediate and heavy nuclei in explosive nuclear burning, even close to stability. PMID:23660558

  8. Direct mass measurements of proton-rich isotopes of Ge, As, Se, and Br

    NASA Astrophysics Data System (ADS)

    Lima, G. F.; Lépine-Szily, A.; Audi, G.; Mittig, W.; Chartier, M.; Orr, N. A.; Lichtenthaler, R.; Angelique, J. C.; Casandjian, J. M.; Cunsolo, A.; Donzaud, C.; Foti, A.; Gillibert, A.; Lewitowicz, M.; Lukyanov, S.; MacCormick, M.; Morrissey, D. J.; Ostrowski, A. N.; Sherrill, B. M.; Stephan, C.; Suomijarvi, T.; Tassan-Got, L.; Vieira, D. J.; Villari, A. C.; Wouters, J. M.

    2002-04-01

    The masses of neutron-deficient nuclei close to the proton drip line are an important input for the rapid proton-capture process modeling above 56Ni. The measurement of the masses of proton-rich nuclei with 32<=Z<=35 has been made using a direct time-of-flight technique. The masses of the nuclides 66As,68Se, and 71Br are reported for the first time, with mass excesses of -51 500(680), -53 620(1000), and -57 060(570) keV being found. The masses agree well in most cases with the Audi-Wapstra systematics.

  9. Decay spectroscopy of exotic nuclei at RIBF

    NASA Astrophysics Data System (ADS)

    Watanabe, H.

    2016-09-01

    Neutron-rich nuclei around the doubly magic nucleus 132Sn and the double midshell nucleus 170Dy have been investigated by means of decay spectroscopy techniques with the EURICA setup at the RIBF facility at RIKEN. The nuclei of interest were produced by in-flight fission of a high-intensity 238U beam at 345 MeV/u. In this contribution, some selected topics are reported.

  10. Octupole shaps in nuclei, and some rotational consequences thereof

    SciTech Connect

    Nazarewicz, W.; Olanders, P.; Ragnarsson, I.; Dudek, J.; Leander, G.A.

    1984-01-01

    During the last years a large number of experimental papers presenting spectroscopic evidence for collective dipole and octupole deformations have appeared. Many theoretical attempts have been made to explain the observed spectroscopic properties in terms of stable octupole deformations. The coupling by the octupole potential, being proportional to Y/sub 30/, is strongest for those subshells for which ..delta..1 = 3. Therefore the tendency towards octupole deformation occurs just beyond closed shells where the high-j intruder subshells (N,1,j) lie very close to the normal parity subshells (N-1,1-3,j-3), i.e. for the particle numbers 34 (g/sub 9/2/-p/sub 3/2/), 56 (h/sub 11/2/-d/sub 5/2/). 9C (i/sub 13/2/-f/sub 7/2/) and 134 (j/sub 15/2/-g/sub 9/2/). Empirically, it is specifically for the particle numbers listed above that negative parity states are observed at relatively low energies in doubly even nuclei. From the different combinations of octupole-driving particle numbers four regions of likely candidates for octupole deformed equilibrium shapes emerge, namely the neutron-deficient nuclei with Z approx. = 90, N approx. = 134 (light actinides) and Z approx. = 34, N approx. = 34 (A approx. = 70) and the neutron-rich nuclei with Z approx. = 56, N approx. = 90 (heavy Ba) and Z approx. = 34, N/sup 56/ (A approx. = 90). In our calculations we searched for octupole unstable nuclei in these four mass regions. The Strutinsky method with the deformed Woods-Saxon potential was employed. The macroscopic part consists of a finite-range liquid drop energy, where both the surface and Coulomb terms contain a diffuseness correction.

  11. IBA for novice experimentalists. I. Introduction to IBA: mostly symmetries. II. Tests in even-even nuclei: mostly transitional systems. III. Supersymmetries: theory and experiment

    SciTech Connect

    Cizewski, J.A.

    1982-08-01

    The report contains the notes from a series of lectures on the Interacting Boson Approximation (IBA) model. The lectures were presented at Lawrence Livermore National Laboratory on July 28, 30 and August 1, 1982 by Jolie A. Cizewski from Yale University. The IBA was developed by F. Iachello and A. Arima starting about seven years ago to understand collective quadrupole excitations in medium and heavy mass nuclei away from closed shells. Since then the formalism has been extended to odd-mass nuclei and considerable work has gone into understanding the microscopic construction of the bosons in this model. The IBA has been applied to nuclei as light as Zn and Ge and as heavy as U and Pu; to nuclei near closed shells, such as Mo and Hg; to stable nuclei and nuclei far from stability. The present lectures were designed to give the experimentalist an introduction to the IBA and to give specific examples of how it could be applied to understand the structure of heavy even and odd mass nuclei. Much of the emphasis was on the symmetries (and supersymmetries) of the model and how the use of symmetries enabled the relatively straightforward understanding of empirical systems as deviations from these symmetries. The richness of possible applications of the IBA to understanding collective phenomena in nuclei was not fully explored, but rather a few illustrative examples were selected and described in detail. The references, accumulated at the end of this report, provide a more comprehensive, although not complete, list of tests of the IBA in even mass nuclei and the new symmetries in odd mass nuclei. The references also list the main theoretical papers which provide the details of the IBA formalism.

  12. Phase diagram and structural diversity of a family of truncated cubes: degenerate close-packed structures and vacancy-rich states.

    PubMed

    Gantapara, Anjan P; de Graaf, Joost; van Roij, René; Dijkstra, Marjolein

    2013-07-01

    Using Monte Carlo simulations and free-energy calculations, we determine the phase diagram of a family of truncated hard cubes, where the shape evolves smoothly from a cube via a cuboctahedron to an octahedron. A remarkable diversity in crystal phases and close-packed structures is found, including a fully degenerate crystal structure, several plastic crystals, as well as vacancy-stabilized crystal phases, all depending sensitively on the precise particle shape. Our results illustrate the intricate relation between phase behavior and building-block shape, and can guide future experimental studies on polyhedral-shaped nanoparticles. PMID:23863011

  13. Functional differentiation in the leucine-rich repeat domains of closely related plant virus-resistance proteins that recognize common avr proteins.

    PubMed

    Sekine, Ken-Taro; Tomita, Reiko; Takeuchi, Shigeharu; Atsumi, Go; Saitoh, Hiromasa; Mizumoto, Hiroyuki; Kiba, Akinori; Yamaoka, Naoto; Nishiguchi, Masamichi; Hikichi, Yasufumi; Kobayashi, Kappei

    2012-09-01

    The N' gene of Nicotiana sylvestris and L genes of Capsicum plants confer the resistance response accompanying the hypersensitive response (HR) elicited by tobamovirus coat proteins (CP) but with different viral specificities. Here, we report the identification of the N' gene. We amplified and cloned an N' candidate using polymerase chain reaction primers designed from L gene sequences. The N' candidate gene was a single 4143 base pairs fragment encoding a coiled-coil nucleotide-binding leucine-rich repeat (LRR)-type resistance protein of 1,380 amino acids. The candidate gene induced the HR in response to the coexpression of tobamovirus CP with the identical specificity as reported for N'. Analysis of N'-containing and tobamovirus-susceptible N. tabacum accessions supported the hypothesis that the candidate is the N' gene itself. Chimera analysis between N' and L(3) revealed that their LRR domains determine the spectrum of their tobamovirus CP recognition. Deletion and mutation analyses of N' and L(3) revealed that the conserved sequences in their C-terminal regions have important roles but contribute differentially to the recognition of common avirulence proteins. The results collectively suggest that Nicotiana N' and Capsicum L genes, which most likely evolved from a common ancestor, differentiated in their recognition specificity through changes in the structural requirements for LRR function.

  14. Systematics of proton and diproton separation energies for light nuclei

    SciTech Connect

    Cole, B.J.

    1997-10-01

    A simple method to estimate proton and two-proton separation energies of proton-rich nuclei is presented that is sufficiently accurate to allow the prediction of suitable candidates for observable diproton decay. The method is based on the systematics of measured particle separation energies. Predictions for proton-rich nuclei with Z=18{minus}24 are compared with the results of previous calculations. {copyright} {ital 1997} {ital The American Physical Society}

  15. IBA in deformed nuclei

    SciTech Connect

    Casten, R.F.; Warner, D.D.

    1982-01-01

    The structure and characteristic properties and predictions of the IBA in deformed nuclei are reviewed, and compared with experiment, in particular for /sup 168/Er. Overall, excellent agreement, with a minimum of free parameters (in effect, two, neglecting scale factors on energy differences), was obtained. A particularly surprising, and unavoidable, prediction is that of strong ..beta.. ..-->.. ..gamma.. transitions, a feature characteristically absent in the geometrical model, but manifest empirically. Some discrepancies were also noted, principally for the K=4 excitation, and the detailed magnitudes of some specific B(E2) values. Considerable attention is paid to analyzing the structure of the IBA states and their relation to geometric models. The bandmixing formalism was studied to interpret both the aforementioned discrepancies and the origin of the ..beta.. ..-->.. ..gamma.. transitions. The IBA states, extremely complex in the usual SU(5) basis, are transformed to the SU(3) basis, as is the interaction Hamiltonian. The IBA wave functions appear with much simplified structure in this way as does the structure of the associated B(E2) values. The nature of the symmetry breaking of SU(3) for actual deformed nuclei is seen to be predominantly ..delta..K=0 mixing. A modified, and more consistent, formalism for the IBA-1 is introduced which is simpler, has fewer free parameters (in effect, one, neglecting scale factors on energy differences), is in at least as good agreement with experiment as the earlier formalism, contains a special case of the 0(6) limit which corresponds to that known empirically, and appears to have a close relationship to the IBA-2. The new formalism facilitates the construction of contour plots of various observables (e.g., energy or B(E2) ratios) as functions of N and chi/sub Q/ which allow the parameter-free discussion of qualitative trajectories or systematics.

  16. Physical processing of cometary nuclei

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.; Stern, S. Alan

    1989-01-01

    Cometary nuclei were formed far from the Sun in the colder regions of the solar nebula, and have been stored in distant orbits in the Oort cloud over most of the history of the solar system. It had been thought that this benign environment would preserve comets in close to their original pristine state. However, recent studies have identified a number of physical processes that have likely acted to modify cometary nuclei in a variety of significant ways. It is important to consider all of these possible processes, both in deciding on a site on the nucleus for collection of cometary samples, and in interpreting the results of analyses of returned cometary samples. Although it can no longer be said that comets are pristine samples of original solar nebula material, they are still the best obtainable samples of that unique period in the formation of the planetary system.

  17. New Isomers in the Neutron-Rich Region Beyond 208Pb

    NASA Astrophysics Data System (ADS)

    Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs.; Pfützner, M.; Regan, P. H.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; de Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R. P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C. L.; Corsi, A.; Bacelar, A. M. Denis; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs.; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Farnea, E.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; John, P. R.; Klupp, S.; Kojouharov, I.; Kurz, N.; Lenzi, S. M.; Leoni, S.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Million, B.; Modamio, V.; Morales, A. I.; Napoli, D. R.; Naqvi, F.; Nicolini, R.; Nociforo, C.; Prochazka, A.; Prokopowicz, W.; Recchia, F.; Ribas, R. V.; Reed, M. W.; Rudolph, D.; Sahin, E.; Schaffner, H.; Sharma, A.; Sitar, B.; Siwal, D.; Steiger, K.; Strmen, P.; Swan, T. P. D.; Szarka, I.; Ur, C. A.; Walker, P. M.; Wieland, O.; Wollersheim, H.-J.

    2014-03-01

    The region of neutron-rich nuclei beyond 208Pb has been very difficult to explore due to its high mass and exoticity. However, recent experimental improvements allowed one to perform a quite extended isomer decay spectroscopy of these nuclei.

  18. Active galactic nuclei

    PubMed Central

    Fabian, Andrew C.

    1999-01-01

    Active galactic nuclei are the most powerful, long-lived objects in the Universe. Recent data confirm the theoretical idea that the power source is accretion into a massive black hole. The common occurrence of obscuration and outflows probably means that the contribution of active galactic nuclei to the power density of the Universe has been generally underestimated. PMID:10220363

  19. Ambartsumyan's concept of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Khachikian, E. Ye.

    2010-01-01

    As Victor Ambartsumyan, himself, noted, the concept of active galactic nuclei occupies a special place among his scientific ideas. It was proposed more than half a century ago and was recognized by the U.S. National Academy of Sciences as revolutionary, on a copernican scale. However, by no means all of its propositions were accepted at once by large parts of the astronomy community. Nevertheless, as the American astrophysicist A. R. Sandage has written, “today, not one astronomer would deny the mystery surrounding the nuclei of galaxies or that the first to recognize the rich reward held in this treasury was Viktor Ambartsumian.” The purpose of this article is to acquaint the reader with the major stages in the formation and development of the concept of active galactic nuclei and with some of the work on this topic done at the Byurakan and other astrophysical observatories throughout the world.

  20. β-Decay Half-Lives of 110 Neutron-Rich Nuclei across the N=82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process.

    PubMed

    Lorusso, G; Nishimura, S; Xu, Z Y; Jungclaus, A; Shimizu, Y; Simpson, G S; Söderström, P-A; Watanabe, H; Browne, F; Doornenbal, P; Gey, G; Jung, H S; Meyer, B; Sumikama, T; Taprogge, J; Vajta, Zs; Wu, J; Baba, H; Benzoni, G; Chae, K Y; Crespi, F C L; Fukuda, N; Gernhäuser, R; Inabe, N; Isobe, T; Kajino, T; Kameda, D; Kim, G D; Kim, Y-K; Kojouharov, I; Kondev, F G; Kubo, T; Kurz, N; Kwon, Y K; Lane, G J; Li, Z; Montaner-Pizá, A; Moschner, K; Naqvi, F; Niikura, M; Nishibata, H; Odahara, A; Orlandi, R; Patel, Z; Podolyák, Zs; Sakurai, H; Schaffner, H; Schury, P; Shibagaki, S; Steiger, K; Suzuki, H; Takeda, H; Wendt, A; Yagi, A; Yoshinaga, K

    2015-05-15

    The β-decay half-lives of 110 neutron-rich isotopes of the elements from _{37}Rb to _{50}Sn were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r-process calculations and reinforce the notion that the second (A≈130) and the rare-earth-element (A≈160) abundance peaks may result from the freeze-out of an (n,γ)⇄(γ,n) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r-process events.

  1. β-Decay Half-Lives of 110 Neutron-Rich Nuclei across the N=82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process.

    PubMed

    Lorusso, G; Nishimura, S; Xu, Z Y; Jungclaus, A; Shimizu, Y; Simpson, G S; Söderström, P-A; Watanabe, H; Browne, F; Doornenbal, P; Gey, G; Jung, H S; Meyer, B; Sumikama, T; Taprogge, J; Vajta, Zs; Wu, J; Baba, H; Benzoni, G; Chae, K Y; Crespi, F C L; Fukuda, N; Gernhäuser, R; Inabe, N; Isobe, T; Kajino, T; Kameda, D; Kim, G D; Kim, Y-K; Kojouharov, I; Kondev, F G; Kubo, T; Kurz, N; Kwon, Y K; Lane, G J; Li, Z; Montaner-Pizá, A; Moschner, K; Naqvi, F; Niikura, M; Nishibata, H; Odahara, A; Orlandi, R; Patel, Z; Podolyák, Zs; Sakurai, H; Schaffner, H; Schury, P; Shibagaki, S; Steiger, K; Suzuki, H; Takeda, H; Wendt, A; Yagi, A; Yoshinaga, K

    2015-05-15

    The β-decay half-lives of 110 neutron-rich isotopes of the elements from _{37}Rb to _{50}Sn were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r-process calculations and reinforce the notion that the second (A≈130) and the rare-earth-element (A≈160) abundance peaks may result from the freeze-out of an (n,γ)⇄(γ,n) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r-process events. PMID:26024165

  2. Major new sources of biological ice nuclei

    NASA Astrophysics Data System (ADS)

    Moffett, B. F.; Hill, T.; Henderson-Begg, S. K.

    2009-12-01

    Almost all research on biological ice nucleation has focussed on a limited number of bacteria. Here we characterise several major new sources of biogenic ice nuclei. These include mosses, hornworts, liverworts and cyanobacteria. Ice nucleation in the eukaryotic bryophytes appears to be ubiquitous. The temperature at which these organisms nucleate is that at which the difference in vapour pressure over ice and water is at or close to its maximum. At these temperatures (-8 to -18 degrees C) ice will grow at the expense of supercooled water. These organisms are dependent for their water on occult precipitation - fog, dew and cloudwater which by its nature is not collected in conventional rain gauges. Therefore we suggest that these organism produce ice nuclei as a water harvesting mechanism. Since the same mechanism would also drive the Bergeron-Findeisen process, and as moss is known to become airborne, these nuclei may have a role in the initiation of precipitation. The properties of these ice nuclei are very different from the well characterised bacterial nuclei. We will also present DNA sequence data showing that, although related, the proteins responsible are only very distantly related to the classical bacterial ice nuclei.

  3. Selfconsistent calculations for hyperdeformed nuclei

    SciTech Connect

    Molique, H.; Dobaczewski, J.; Dudek, J.; Luo, W.D.

    1996-12-31

    Properties of the hyperdeformed nuclei in the A {approximately} 170 mass range are re-examined using the self-consistent Hartree-Fock method with the SOP parametrization. A comparison with the previous predictions that were based on a non-selfconsistent approach is made. The existence of the {open_quotes}hyper-deformed shell closures{close_quotes} at the proton and neutron numbers Z=70 and N=100 and their very weak dependence on the rotational frequency is suggested; the corresponding single-particle energy gaps are predicted to play a role similar to that of the Z=66 and N=86 gaps in the super-deformed nuclei of the A {approximately} 150 mass range. Selfconsistent calculations suggest also that the A {approximately} 170 hyperdeformed structures have neglegible mass asymmetry in their shapes. Very importantly for the experimental studies, both the fission barriers and the {open_quotes}inner{close_quotes} barriers (that separate the hyperdeformed structures from those with smaller deformations) are predicted to be relatively high, up to the factor of {approximately}2 higher than the corresponding ones in the {sup 152}Dy superdeformed nucleus used as a reference.

  4. Exotic Light Nuclei

    ERIC Educational Resources Information Center

    Cerny, Joseph; Poskanzer, Arthur M.

    1978-01-01

    Among the light elements, nuclei with unequal numbers of protons and neutrons are highly unstable. Some survive just long enough to be detected and exhibit unusual regimes of radioactive decay. ( Autor/MA)

  5. Radiations from hot nuclei

    NASA Technical Reports Server (NTRS)

    Malik, F. Bary

    1993-01-01

    The investigation indicates that nuclei with excitation energy of a few hundred MeV to BeV are more likely to radiate hot nuclear clusters than neutrons. These daughter clusters could, furthermore, de-excite emitting other hot nuclei, and the chain continues until these nuclei cool off sufficiently to evaporate primarily neutrons. A few GeV excited nuclei could radiate elementary particles preferentially over neutrons. Impact of space radiation with materials (for example, spacecraft) produces highly excited nuclei which cool down emitting electromagnetic and particle radiations. At a few MeV excitation energy, neutron emission becomes more dominant than gamma-ray emission and one often attributes the cooling to take place by successive neutron decay. However, a recent experiment studying the cooling process of 396 MeV excited Hg-190 casts some doubt on this thinking, and the purpose of this investigation is to explore the possibility of other types of nuclear emission which might out-compete with neutron evaporation.

  6. Scattering Of Light Nuclei

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R

    2009-12-15

    The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches.We present a new ab initio many-body approach which derives from the combination of the ab initio no-core shell model with the resonating-group method [4]. By complementing a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters, this approach is capable of describing simultaneously both bound and scattering states in light nuclei. We will discuss applications to neutron and proton scattering on sand light p-shell nuclei using realistic nucleon-nucleon potentials, and outline the progress toward the treatment of more complex reactions.

  7. Response of hot nuclei

    SciTech Connect

    Broglia, R.A.

    1986-01-01

    The dipole giant resonance is reviewed, as it is the only vibration which has been experimentally identified in the decay of hot nuclei. The mechanism of exciting the resonance and the mode of the resonance are described. The methods used to calculate the vibrations from the shell model are discussed, including the Hartree-Fock approximation and random phase approximation. Nuclei formed by compound nuclear reactions, which possess high excitation energy and angular momentum, are considered. It is argued that the stability of the dipole may be used to advantage in the study of other properties of nuclei at high excitation. It is also considered possible that the discussion of the dipole giant resonance may be extended to the gamma decay of the isovector quadrupole vibration. 26 refs., 18 figs. (LEW)

  8. Four-body correlations in nuclei.

    PubMed

    Sambataro, M; Sandulescu, N

    2015-09-11

    Low-energy spectra of 4n nuclei are described with high accuracy in terms of four-body correlated structures ("quartets"). The states of all N≥Z nuclei belonging to the A=24 isobaric chain are represented as a superposition of two-quartet states, with quartets being characterized by isospin T and angular momentum J. These quartets are assumed to be those describing the lowest states in ^{20}Ne (T_{z}=0), ^{20}F (T_{z}=1), and ^{20}O (T_{z}=2). We find that the spectrum of the self-conjugate nucleus ^{24}Mg can be well reproduced in terms of T=0 quartets only and that, among these, the J=0 quartet plays by far the leading role in the structure of the ground state. The same conclusion is drawn in the case of the three-quartet N=Z nucleus ^{28}Si. As an application of the quartet formalism to nuclei not confined to the sd shell, we provide a description of the low-lying spectrum of the proton-rich ^{92}Pd. The results achieved indicate that, in 4n nuclei, four-body degrees of freedom are more important and more general than usually expected. PMID:26406824

  9. Band structures in light neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Bohlen, H. G.; von Oertzen, W.; Kalpakchieva, R.; Massey, T. N.; Dorsch, T.; Milin, M.; Schulz, C.; Kokalova, T.; Wheldon, C.

    2008-05-01

    The structure of beryllium isotopes in the mass range A = 8-12 has been investigated using the properties of different bands, which are populated in specific reactions. The different structures are formed in transfer reactions with neutron stripping on 9,10Be or proton pick-up on 12,13,14C. The slope in the linear dependence of the excitation energies on J(J+1), where J is the spin, has been deduced for 13 bands and compared for common systematics. From the measured moments-of-inertia the α - α distance has been deduced for molecular structures.

  10. Beta Decay Spectroscopy of Neutron-Rich Nuclei at RIBF

    NASA Astrophysics Data System (ADS)

    Lorusso, G.; Nishimura, S.; Baba, H.; Doornenbal, P.; Isobe, T.; Söderström, P.-A.; Browne, F.; Daido, R.; Yifan, F.; Nishibata, H.; Yagi, A.; Gey, G.; Li, Z.; Wu, J.; Lubos, D.; Moschner, K.; Patel, Z.; Rice, S.; Sinclair, L.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Watanabe, H.; Xu, Z. Y.; Yoshinaga, K.

    2015-11-01

    The development of a high intensity 238U beam at the Radioactive Isotope Beam Factory (RIBF) has opened a new opportunity to explore exotic regions of the nuclear chart that were not accessible before. Along with beam development, the installation of the high efficiency γ-detector EURICA has made β-decay spectroscopy measurements of these regions possible, and a large international effort named the EURICA project has been launched to take advantage of this new opportunity.

  11. New type of asymmetric fission in proton-rich nuclei.

    PubMed

    Andreyev, A N; Elseviers, J; Huyse, M; Van Duppen, P; Antalic, S; Barzakh, A; Bree, N; Cocolios, T E; Comas, V F; Diriken, J; Fedorov, D; Fedosseev, V; Franchoo, S; Heredia, J A; Ivanov, O; Köster, U; Marsh, B A; Nishio, K; Page, R D; Patronis, N; Seliverstov, M; Tsekhanovich, I; Van den Bergh, P; Van De Walle, J; Venhart, M; Vermote, S; Veselsky, M; Wagemans, C; Ichikawa, T; Iwamoto, A; Möller, P; Sierk, A J

    2010-12-17

    A very exotic process of β-delayed fission of 180Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the fission-fragment mass distribution of the post-β-decay daughter nucleus 180Hg (N/Z=1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two 90Zr fragments, with magic N=50 and semimagic Z=40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly measured branching ratio for β-delayed fission of 180Tl is 3.6(7) × 10(-3)%, approximately 2 orders of magnitude larger than in an earlier study. PMID:21231583

  12. Exotic structure in light neutron-rich nuclei

    SciTech Connect

    Itagaki, N.; Zhao, P. W.; Meng, J.; Matsuno, H.; Suhara, T.

    2015-10-15

    In this presentation I discussed two subjects. One is the persistence of threefold symmetry in the ground state of {sup 12}C. Recently D{sub 3h} symmetry has been established in {sup 12}C, which reflects the geometric symmetry of the three α particles. Although the spin-orbit interaction plays a significant role and this interaction breaks the α clusters, we show that threefold symmetry of {sup 12}C is still there. We use AQCM approach and discuss that inclusion of spin-orbit interaction, which is absent in the conventional microscopic α cluster models, is possible keeping the threefold symmetry. The second subject is the appearance of rod shape in C isotopes, which has been investigated in the framework of the cranking covariant density functional theory. The relationship between the stability of such states and the spin and isospin degrees of freedom is discussed; adding valence neutrons and rotating the system. These two effects stabilize the rod shape, and in addition, their coherent effect has been found; the σ-orbits (parallel to the symmetry axis) of the valence neutrons, which enhances the rod shape, is lowered by the rotation of the system, and this σ-orbit pulls down the single particle energies of protons with linear configuration owing to the proton-neutron interaction effect.

  13. Stellar (n, gamma) cross sections of neutron-rich nuclei

    SciTech Connect

    Marganiec, J.; Domingo Pardo, C.; Kaeppeler, F.

    2010-03-01

    The present measurements were performed by means of the activation technique. Neutrons were produced at the Karlsruhe Van de Graaff accelerator via the {sup 7}Li(p,n){sup 7}Be reaction. For proton energies just above threshold, one obtains a neutron spectrum similar to a Maxwellian distribution for kT = 25 keV. This quasi-stellar neutron spectrum allowed us to measure the Maxwellian averaged cross sections directly. The experimental results of {sup 174,176}Yb, {sup 184,186}W, {sup 190,192}Os, {sup 196,198}Pt, and {sup 202}Hg were extrapolated from kT = 25 keV to lower and higher temperatures.

  14. Experiments with neutron-rich isomeric beams

    SciTech Connect

    Rykaczewski, K. |; Grzywacz, R. |; Lewitowicz, M.; Pfuetzner, M.; Grawe, H.

    1998-01-01

    A review of experimental results obtained on microsecond-isomeric states in neutron-rich nuclei produced in fragmentation reactions and studied with SISSI-Alpha-LISE3 spectrometer system at GANIL Caen is given. The perspectives of experiments based on secondary reactions with isomeric beams are presented.

  15. Electromagnetic structure of nuclei

    SciTech Connect

    Arnold, R.G.

    1986-07-01

    A brief review is given of selected topics in the electromagnetic structure of nucleons and nuclei, including nucleon form factors from both quantum chromodynamics and electron scattering data, measurements of the deuteron and triton form factors, quasi-elastic scattering, and the EMC effect. 47 refs., 13 figs. (LEW)

  16. Quark structure of nuclei

    SciTech Connect

    Blankenbecler, R.

    1981-01-01

    A brief review is given of selected topics involved in the relativistic quark structure of nuclei such as the infinite momentum variables, scaling variables, counting rules, forward-backward variables, thermodynamic-like limit, QCD effects, higher quark bags, confinement, and many unanswered questions.

  17. Transfer involving deformed nuclei

    SciTech Connect

    Rasmussen, J.O.; Guidry, M.W.; Canto, L.F.

    1985-03-01

    Results are reviewed of 1- and 2-neutron transfer reactions at near-barrier energies for deformed nuclei. Rotational angular momentum and excitation patterns are examined. A strong tendency to populating high spin states within a few MeV of the yrast line is noted, and it is interpreted as preferential transfer to rotation-aligned states. 16 refs., 12 figs.

  18. Cluster aspects of p-shell and sd-shell nuclei

    SciTech Connect

    Kanada-En'yo, Y.; Kobayashi, F.; Suhara, T.; Kimura, M.; Taniguchi, Y.

    2011-05-06

    We report some topics on cluster structures studied by using a theoretical method of antisymmetrized molecular dynamics(AMD). Cluster features of p-shell and sd-shell nuclei are discussed. In particular, three alpha cluster structures in the excited states of {sup 12}C and {sup 14}C are focused. Dineutron correlations in neutron-rich nuclei are also discussed.

  19. Energetic Nuclei, Superdensity and Biomedicine

    ERIC Educational Resources Information Center

    Baldin, A. M.

    1977-01-01

    High-energy, relativistic nuclei were first observed in cosmic rays. Studing these nuclei has provided an opportunity for analyzing the composition of cosmic rays and for experimentally verifying principles governing the behavior of nuclear matter at high and super-high temperatures. Medical research using accelerated nuclei is suggested.…

  20. Mass extrapolations in the region of deformed rare Earth nuclei

    SciTech Connect

    Borcea, C.; Audi, G.

    1998-12-21

    A procedure based on the regularity property of the mass surface is proposed to make predictions for the masses of neutron rich deformed nuclei in the rare earth region. Tables are given for the estimated masses; they extend up to the presumed limit of the deformation region.

  1. Light element production by low energy nuclei from massive stars

    NASA Technical Reports Server (NTRS)

    Vangioni-Flam, E.; Casse, M.; Ramaty, R.

    1997-01-01

    The Orion complex is a source of gamma rays attributed to the de-excitation of fast carbon and oxygen nuclei excited through interactions with ambient hydrogen and helium. This has consequences for the production and evolution of light isotopes in the Galaxy, as massive stars appear as prolific sources of C-O rich low energy nuclei. The different stages of massive star evolution are considered in relation to the acceleration of nuclei to moderate energies. It is concluded that the low energy nuclear component originating from massive stars plays a larger role than the usual Galactic cosmic rays in shaping the evolution of Li-6, Be-9, B-10 and B-11, especially in the early Galactic evolution. The enhancement of the B-11/B-10 ratio observed in meteorites and in the interstellar medium is attributed to the interaction of low energy carbon nuclei with ambient H and to a lesser degree, to neutrino spallation.

  2. Reactions and structure of exotic nuclei

    SciTech Connect

    Esbensen, H.

    1993-08-01

    Radioactive beam experiments have made it possible to study the structure of light neutron rich nuclei. A characteristic feature is a large dipole strength near threshold. An excellent example is the loosely bound nucleus ``Li for which Coulomb dissociation plays a dominant role in breakup reactions on a high Z target. I will describe a three-body model and apply it to calculate the dipole response of {sup 11}Li and the momentum distributions for the three-body breakup reaction: {sup 11}Li {yields} {sup 9}Li+n+n, and comparisons will be made to recent three-body coincidence measurements.

  3. τ- capture in nuclei

    NASA Astrophysics Data System (ADS)

    Chiang, Huan, Ching; Oset, Eulogio

    1991-04-01

    We determine the capture rate of a τ- from inner atomic orbits in medium and heavy nuclei through the reaction τ-p-->nvτ, The capture rates are of the order of 2×109 s-1, a factor 150 larger than the muon capture rates in heavy nuclei, and three orders of magnitude smaller than the ordinary free τ- width. The investigatiion of this and related τ- capture channels would allow the exploration of the nuclear excitation mechanisms in an unsusual regime of momentum transfer and would provide valuable information on the axial form factor of the nucleon at large momentum transfer. Permanent address: Departmento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia - CSIC, E-46100 Burjassot (Valencia) Spain.

  4. Nuclei in Astrophysics

    NASA Astrophysics Data System (ADS)

    Penionzhkevich, Yu. E.

    2016-06-01

    This work is an attempt to present some problems on the evolution of the Universe: the nucleosynthesis and cosmochronology from the standpoint of physics of particles and nuclei, in particular with the use of the latest results, obtained by means of radioactive nuclear beams. The comparison is made between the processes taking place in the Universe and the mechanisms of formation and decay of nuclei, as well as of their interaction at different energies. Examples are given to show the capabilities of nuclearphysics methods for studying cosmic objects and properties of the Universe. The results of investigations in nuclear reactions, induced by radioactive nuclear beams, make it possible to analyze the nucleosynthesis scenario in the region of light elements in a new manner.

  5. Pairing forces in nuclei

    SciTech Connect

    Chasman, R.R.

    1996-12-31

    In this contribution, the author mentions some features of pairing forces that are unique to nuclei and cover some areas of major interest in nuclear structure research, that involve pairing. At the level of most nuclear structure studies, nuclei are treated as consisting of two kinds of fermions (protons and neutrons) in a valence space with rather few levels. These features give rise to unique aspects of pairing forces in nuclei: (1) n-p pairing in T = 0 as well as the usual T = 1 pairing that is characteristic of like fermions; (2) a need to correct pairing calculations for the (1/N) effects that can typically be neglected in superconducting solids. An issue of current concern is the nature of the pairing interaction: several recent studies suggest a need for a density dependent form of the pairing interaction. There is a good deal of feedback between the questions of accurate calculations of pairing interactions and the form and magnitude of the pairing interaction. Finally, the authors discuss some many-body wave functions that are a generalization of the BCS wave function form, and apply them to a calculation of energy level spacings in superdeformed rotational bands.

  6. Coupled-Channel Computation of Direct Neutron Capture on Non-Spherical Nuclei

    NASA Astrophysics Data System (ADS)

    Arbanas, Goran; Thompson, Ian; Escher, Jutta; Nunes, Filomena; Elster, Charlotte; Zhang, Shi-Sheng

    2014-09-01

    Models of direct neutron capture of neutrons have so far accounted for the effects of non-spherical nuclei either in the incoming wave functions (via non-spherical optical model potentials), or in the final bound states (via non-spherical real potential wells), but not in both. Since it is known that spherical optical potentials do not give a good reproduction of low energy neutron-scattering observables of deformed nuclei, we have performed calculations in which the initial and final states are both treated in a self-consistent, non-spherical-nucleus picture. We have done this in the coupled-channels model of nuclear reactions implemented in the FRESCO code by using the same deformation-length for the couplings to the rotational-band states in the incoming and the final state configurations. We compute direct capture using this method for even-mass calcium isotopes 40 , 42 , 44 , 46 , 48Ca to study the effect across the two closed neutron shells, for neutron-rich even-mass tin isotopes relevant to models of astrophysical nucleosynthesis, and for 56Fe that is an important structural material used in nuclear applications. Models of direct neutron capture of neutrons have so far accounted for the effects of non-spherical nuclei either in the incoming wave functions (via non-spherical optical model potentials), or in the final bound states (via non-spherical real potential wells), but not in both. Since it is known that spherical optical potentials do not give a good reproduction of low energy neutron-scattering observables of deformed nuclei, we have performed calculations in which the initial and final states are both treated in a self-consistent, non-spherical-nucleus picture. We have done this in the coupled-channels model of nuclear reactions implemented in the FRESCO code by using the same deformation-length for the couplings to the rotational-band states in the incoming and the final state configurations. We compute direct capture using this method for even

  7. Shell states of neutron-rich matter

    NASA Astrophysics Data System (ADS)

    Horowitz, C. J.; Shen, G.

    2008-07-01

    The equation of state (EOS) for nuclear and neutron rich matter is investigated in a relativistic mean field (RMF) model. New shell states are found that minimize the free energy per baryon, calculated in a spherical Wigner-Seitz (WS) approximation, over a significant range of baryon densities. These shell states, that have both inside and outside surfaces, minimize the Coulomb energy of large proton number configurations at the expense of a larger surface energy. This is related to a possible depression in the central density of super heavy nuclei. As the baryon density increases, we find the system changes from normal nuclei, to shell states, and then to uniform matter.

  8. Shell states of neutron-rich matter

    SciTech Connect

    Horowitz, C. J.; Shen, G.

    2008-07-15

    The equation of state (EOS) for nuclear and neutron rich matter is investigated in a relativistic mean field (RMF) model. New shell states are found that minimize the free energy per baryon, calculated in a spherical Wigner-Seitz (WS) approximation, over a significant range of baryon densities. These shell states, that have both inside and outside surfaces, minimize the Coulomb energy of large proton number configurations at the expense of a larger surface energy. This is related to a possible depression in the central density of super heavy nuclei. As the baryon density increases, we find the system changes from normal nuclei, to shell states, and then to uniform matter.

  9. Fusion excitation functions involving transitional nuclei

    SciTech Connect

    Rehm, K.E.; Jiang, C.L.; Esbensen, H.

    1995-08-01

    Measurements of fusion excitation functions involving transitional nuclei {sup 78}Kr and {sup 100}Mo showed a different behavior at low energies, if compared to measurements with {sup 86}Kr and {sup 92}Mo. This points to a possible influence of nuclear structure on the fusion process. One way to characterize the structure of vibrational nuclei is via their restoring force parameters C{sub 2} which can be calculated from the energy of the lowest 2{sup +} state and the corresponding B(E2) value. A survey of the even-even nuclei between A = 28-150 shows strong variations in C{sub 2} values spanning two orders of magnitude. The lowest values for C{sub 2} are observed for {sup 78}Kr, {sup 104}Ru and {sup 124}Xe followed by {sup 74,76}Ge, {sup 74,76}Se, {sup 100}Mo and {sup 110}Pd. In order to learn more about the influence of {open_quotes}softness{close_quotes} on the sub-barrier fusion enhancement, we measured cross sections for evaporation residue production for the systems {sup 78}Kr + {sup 104}Ru and {sup 78}Kr + {sup 76}Ge with the gas-filled magnet technique. For both systems, fusion excitation functions involving the closed neutron shell nucleus {sup 86}Kr were measured previously. The data are presently being analyzed.

  10. Microscopic and self-consistent description for neutron halo in deformed nuclei

    SciTech Connect

    Li Lulu; Meng Jie; Zhao Enguang; Zhou Shangui

    2013-05-06

    A deformed relativistic Hartree-Bogoliubov theory in continuum has been developed for the study of neutron halos in deformed nuclei and the halo phenomenon in deformed weakly bound nuclei is investigated. Magnesium and neon isotopes are studied and some results are presented for the deformed neutron-rich and weakly bound nuclei {sup 44}Mg and {sup 36}Ne. The core of the former nucleus is prolate, but the halo has a slightly oblate shape. This indicates a decoupling of the halo orbitals from the deformation of the core. The generic conditions for the existence of halos in deformed nuclei and for the occurrence of this decoupling effect are discussed.

  11. Quantitative microspectral evaluation of the ratio of arginine-rich to lysine-rich histones in neurons and neuroglial cells.

    PubMed

    Pevzner, L Z; Raygorodskaya, T G; Agroskin, L S

    1978-09-01

    Staining of nervous tissue sections with ammoniacal silver according to Black et al. has been confirmed to be a reliable histochemical colour reaction for quantitative evaluation of arginine-rich and lysine-rich histones in cell structures on the basis of determinations of the position of spectral curve maximum. Neurons of several brain nuclei which differed in predominating neurotransmitter did not differ in the ratio of arginine-rich to lysine-rich histones while some differences in this ratio were found out in the glial satelite cells adjacent to the corresponding neurons of these nuclei. Moderate circadian fluctuations were observed in the arginine-rich to lysine-rich histone ratio, these fluctuations being rather similar in the neurons studied and in the cells of perineuronal neuroglia.

  12. Properties of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Rahe, J.; Vanysek, V.; Weissman, P. R.

    1994-01-01

    Active long- and short-period comets contribute about 20 to 30 % of the major impactors on the Earth. Cometary nuclei are irregular bodies, typically a few to ten kilometers in diameter, with masses in the range 10(sup 15) to 10(sup 18) g. The nuclei are composed of an intimate mixture of volatile ices, mostly water ice and hydrocarbon and silicate grains. The composition is the closest to solar composition of any known bodies in the solar system. The nuclei appear to be weakly bonded agglomerations of smaller icy planetesimals, and material strengths estimated from observed tidal disruption events are fairly low, typically 10(sup 2) to 10(sup 4) N m(sup -2). Density estimates range between 0.2 and 1.2 g cm(sup -3) but are very poorly determined, if at all. As comets age they develop nonvolitile crusts on their surfaces which eventually render them inactive, similar in appearance to carbonaceous asteroids. However, dormant comets may continue to show sporadic activity and outbursts for some time before they become truly extinct. The source of the long-period comets is the Oort cloud, a vast spherical cloud of perhaps 10(sup 12) to 10(sup 13) comets surrounding the solar system and extending to interstellar distances. The likely source for short-period comets is the Kuiper belt. a ring of perhaps 10(sup 8) to 10(sup 10) remnant icy planetesimals beyond the orbit of Neptune, though some short-period comets may also be long-period comets from the Oort cloud which have been perturbed into short-period orbits.

  13. Thermal evolution of cometary nuclei

    NASA Astrophysics Data System (ADS)

    Prialnik, D.

    2014-07-01

    Thermal modeling of comet nuclei and similar objects involves the solution of conservation equations for energy and masses of the various components over time. For simplicity, the body is generally, but not necessarily, assumed to be of spherical shape. The processes included in such calculations are heat transfer, gas flow, dust drag, phase transitions, internal heating by various sources, internal structure alterations, surface sublimation. Physical properties --- such as the thermal conductivity, permeability, material strength, and porous structure --- are assumed, based on the best available estimates from laboratory experiments and space-mission results. Calculations employ various numerical procedures and require significant computational power, data analysis, and often sophisticated methods of graphical presentation. They start with a body of given size, mass, and composition, as well as a given orbit. The results yield properties and activity patterns that can be confronted with observations. Initial parameters may be adjusted until agreement is achieved. A glimpse into the internal structure of the object, which is inaccessible to direct observation, is thus obtained. The last decade, since the extensive overview of the subject was published (Modeling the structure and activity of comet nuclei, Prialnik, D.; Benkhoff, J.; Podolak, M., in Comets II, M. C. Festou, H. U. Keller, and H. A. Weaver, eds., University of Arizona Press, Tucson, p.359-387), thermal modeling has significantly advanced. This was prompted both by new properties and phenomena gleaned from observations, one example being main-belt comets, and the continual increase in computational power and performance. Progress was made on two fronts. On the computational side, multi-dimensional models have been developed, adaptive-grid and moving-boundaries techniques have been adopted, and long-term evolutionary calculations have become possible, even spanning the lifetime of the Solar System. On

  14. Electroproduction of Strange Nuclei

    SciTech Connect

    E.V. Hungerford

    2002-06-01

    The advent of high-energy, CW-beams of electrons now allows electro-production and precision studies of nuclei containing hyperons. Previously, the injection of strangeness into a nucleus was accomplished using secondary beams of mesons, where beam quality and target thickness limited the missing mass resolution. We review here the theoretical description of the (e, e'K+) reaction mechanism, and discuss the first experiment demonstrating that this reaction can be used to precisely study the spectra of light hypernuclei. Future experiments based on similar techniques, are expected to attain even better resolutions and rates.

  15. Damping in Yb nuclei

    SciTech Connect

    Stephens, F.S.; Deleplanque, M.A.; Lee, I.Y.; Ward, D.; Fallon, P.; Cromaz, M.; Macchiavelli, A.O.; Clark, R.M.; Diamond, R.M.; Gorgen, A.

    2002-07-01

    In a mixture of three Yb nuclei, we find the rotational damping widths vary from 180 keV at 1.1 MeV {gamma}-ray energy to 290 keV at 1.5 MeV, and the average compound damping widths (or spreading widths) vary from 40 keV at 1.1 MeV {gamma}-ray energy to 60 keV at 1.3 MeV. The simulations also suggest extensive motional narrowing.

  16. Electron Scattering from Nuclei

    SciTech Connect

    J. Wallace Van Orden

    2002-08-01

    The description of nuclei at distances on the order of a fermi or less poses a difficult challenge for theoretical physicists. At larger distances the traditional description of the nucleus as a collection of interacting nucleons has been quite successful and substantial progress has been made in recent years in describing few-nucleon systems using this approach. However, it has been known for several decades that the nucleons themselves are composite objects which are believed to be described by Quantum Chromodynamics (QCD). QCD is a complicated nonlinear strongly interacting field theory which can only be used for calculation in special circumstances. Due to the property of asymptotic freedom exhibited by QCD, perturbative calculations of QCD can be made at large momentum transfers and have achieved substantial success for a variety of processes. Understanding the transition from traditional pictures of nuclei to QCD is a substantial challenge. As an example of this problem, this paper describes recent calculations of elastic electron-deuteron scattering based on a relativistic extension of the traditional nuclear physics approach. The results of this work are compared to new data obtained at the Thomas Jefferson National Laboratory and to the predictions of perturbative QCD.

  17. Exotic nuclei in astrophysics

    NASA Astrophysics Data System (ADS)

    Penionzhkevich, Yu. E.

    2012-07-01

    Recently the academic community has marked several anniversaries connected with discoveries that played a significant role in the development of astrophysical investigations. The year 2009 was proclaimed by the United Nations the International Year of Astronomy. This was associated with the 400th anniversary of Galileo Galilei's discovery of the optical telescope, which marked the beginning of regular research in the field of astronomy. An important contribution to not only the development of physics of the microcosm, but also to the understanding of processes occurring in the Universe, was the discovery of the atomic nucleus made by E. Rutherford 100 years ago. Since then the investigations in the fields of physics of particles and atomic nuclei have helped to understand many processes in the microcosm. Exactly 80 years ago, K. Yanski used a radio-telescope in order to receive the radiation from cosmic objects for the first time, and at the present time this research area of physics is the most efficient method for studying the properties of the Universe. Finally, the April 12, 1961 (50 years ago) launching of the first sputnik into space with a human being onboard, the Russian cosmonaut Yuri Gagarin, marked the beginning of exploration of the Universe with the direct participation of man. All these achievements considerably extended our ideas about the Universe. This work is an attempt to present some problems on the evolution of the Universe: the nucleosynthesis and cosmochronology from the standpoint of physics of particles and nuclei, in particular with the use of the latest results, obtained by means of radioactive nuclear beams. The comparison is made between the processes taking place in the Universe and the mechanisms of formation and decay of nuclei, as well as of their interaction at different energies. Examples are given to show the capabilities of nuclear-physics methods for studying cosmic objects and properties of the Universe. The results of

  18. Probing neutron rich matter with parity violation

    NASA Astrophysics Data System (ADS)

    Horowitz, Charles

    2016-03-01

    Many compact and energetic astrophysical systems are made of neutron rich matter. In contrast, most terrestrial nuclei involve approximately symmetric nuclear matter with more equal numbers of neutrons and protons. However, heavy nuclei have a surface region that contains many extra neutrons. Precision measurements of this neutron rich skin can determine properties of neutron rich matter. Parity violating electron scattering provides a uniquely clean probe of neutrons, because the weak charge of a neutron is much larger than that of a proton. We describe first results and future plans for the Jefferson Laboratory experiment PREX that measures the thickness of the neutron skin in 208Pb. Another JLAB experiment CREX will measure the neutron radius of 48Ca and test recent microscopic calculations of this neutron rich 48 nucleon system. Finally, we show how measuring parity violation at multiple momentum transfers can determine not just the neutron radius but the full radial structure of the neutron density in 48Ca. A neutron star is eighteen orders of magnitude larger than a nucleus (km vs fm) but both the star and the neutron rich nuclear skin are made of the same neutrons, with the same strong interactions, and the same equation of state. A large pressure pushes neutrons out against surface tension and gives a thick neutron skin. Therefore, PREX will constrain the equation of state of neutron rich matter and improve predictions for the structure of neutron stars. Supported in part by DOE Grants DE-FG02-87ER40365 (Indiana University) and DE-SC0008808 (NUCLEI SciDAC Collaboration).

  19. Quarks in Few Body Nuclei

    NASA Astrophysics Data System (ADS)

    Holt, Roy J.

    2016-03-01

    Electron scattering at very high Bjorken x from hadrons provides an excellent test of models, has an important role in high energy physics, and from nuclei, provides a window into short range correlations. Light nuclei have a key role because of the relatively well-known nuclear structure. The development of a novel tritium target for Jefferson Lab has led to renewed interest in the mass three system. For example, deep inelastic scattering experiments in the light nuclei provide a powerful means to determine the neutron structure function. The isospin dependence of electron scattering from mass-3 nuclei provide information on short range correlations in nuclei. The program using the new tritium target will be presented along with a summary of other experiments aimed at revealing the large-x structure of the nucleon.

  20. Isolation of nuclei from yeast.

    PubMed

    Bhargava, M M; Halvorson, H O

    1971-05-01

    A method for isolation of nuclei from Saccharomyces cervisiae in high yield is described. The DNA/protein ratio of the isolated nuclei is 10 times higher than that of whole cells. Examination of these nuclei in phase and electron microscopes has shown them to be round bodies having a double membrane, microtubules, and a dark crescent at one end. The optimum conditions for extraction and resolution of histones of these nuclei on acrylamide gels have been investigated. The nuclei have an active RNA polymerase (E.C. 2.7.7.6) and are able to synthesize RNA in vitro. They are also readily stainable with Giemsa's, Feulgen's, and acridine orange methods. PMID:19866769

  1. Concentrations of condensation nuclei in the vicinity of jetstream maxima

    NASA Technical Reports Server (NTRS)

    Cadle, R. D.; Shapiro, M. A.; Langer, G.

    1979-01-01

    Ozone and condensation nuclei were measured on March 29, 1977 (and March 30, GMT) from a Sabreliner in a frontal zone south of Denver, Colo. The ozone served as a tracer for stratospheric air and the condensation nuclei as a tracer for tropospheric air. Both the Langer condensation nucleus counter and the Rich-100 counter can be used to measure condensation nucleus concentrations in the vicinity of the tropopause. However, the former counter is more sensitive to low concentrations. The nuclei measured were found to be almost entirely larger than 0.005 micron in radius, consisting of thousands of molecules. The mesostructure of the ozone and condensation nucleus concentrations agreed well with a double structure of the frontal zone that became apparent from a detailed analysis of radiosonde data.

  2. Formation of superheavy nuclei in cold fusion reactions

    SciTech Connect

    Feng Zhaoqing; Jin Genming; Li Junqing; Scheid, Werner

    2007-10-15

    Within the concept of the dinuclear system (DNS), a dynamical model is proposed for describing the formation of superheavy nuclei in complete fusion reactions by incorporating the coupling of the relative motion to the nucleon transfer process. The capture of two heavy colliding nuclei, the formation of the compound nucleus, and the de-excitation process are calculated by using an empirical coupled channel model, solving a master equation numerically and applying statistical theory, respectively. Evaporation residue excitation functions in cold fusion reactions are investigated systematically and compared with available experimental data. Maximal production cross sections of superheavy nuclei in cold fusion reactions with stable neutron-rich projectiles are obtained. Isotopic trends in the production of the superheavy elements Z=110, 112, 114, 116, 118, and 120 are analyzed systematically. Optimal combinations and the corresponding excitation energies are proposed.

  3. Description of Exotic Nuclei with the Interacting Boson Model

    SciTech Connect

    Boeyuekata, M.; Van Isacker, P.; Uluer, I.

    2008-11-11

    Even--even nuclei in the A{approx}100 mass region are investigated within the framework of the interacting boson model-1 (IBM-1). The study includes energy spectra and electric quadrupole transition properties of zirconium, molybdenum, ruthenium and palladium isotopes with neutron number N{>=}54. A global parametrization of the IBM-1 hamiltonian is found leading to a description of 301 collective levels in 30 nuclei with a root-mean-square deviation from the observed level energies of 119 keV. The geometric character of the nuclei can be visualized by plotting the potential energy surface V({beta},{gamma}) obtained from the IBM-1 hamiltonian in the classical limit. The parametrization established on the basis of known elements is then used to predict properties of the unknown, neutron-rich isotopes {sup 106}Zr, {sup 112}Mo, {sup 116}Ru and {sup 120}Pd.

  4. Fission of actinide nuclei using multi-nucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Léguillon, Romain; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Makii, Hiroyuki; Nishinaka, Ichiro; Ishii, Tetsuro; Tsukada, Kazuaki; Asai, Masato; Chiba, Satoshi; Ohtsuki, Tsutomu; Araki, Shohei; Watanabe, Yukinobu; Tatsuzawa, Ryotaro; Takaki, Naoyuki

    2014-09-01

    We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. Present study is supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan.

  5. Effect of properties of superheavy nuclei on their production and decay

    NASA Astrophysics Data System (ADS)

    Adamian, G. G.; Antonenko, N. V.; Bezbakh, A. N.; Jolos, R. V.

    2016-05-01

    Properties and stability of superheavy nuclei resulting from hot fusion are discussed. It is shown that the microscopic-macroscopic approach allows obtaining the closed proton shell at Z ≥ 120. Isotopic trends of K-isomeric states in superheavy nuclei are predicted. Evaporation residue cross sections in hot fusion reactions are calculated using the predicted properties of superheavy nuclei. Interruption of α decay chains by spontaneous fission is analyzed. Alpha decay chains through isomeric states are considered. Internal level densities in superheavy nuclei are microscopically calculated.

  6. Nuclei at extreme conditions. A relativistic study

    SciTech Connect

    Afanasjev, Anatoli

    2014-11-14

    The major goals of the current project were further development of covariant density functional theory (CDFT), better understanding of its features, its application to different nuclear structure and nuclear astrophysics phenomena and training of graduate and undergraduate students. The investigations have proceeded in a number of directions which are discussed in detail in the part “Accomplishments” of this report. We have studied the role of isovector and isoscalar proton-neutron pairings in rotating nuclei; based on available experimental data it was concluded that there are no evidences for the existence of isoscalar proton-neutron pairing. Generalized theoretical approach has been developed for pycnonuclear reaction rates in the crust of neutron stars and interior of white dwarfs. Using this approach, extensive database for considerable number of pycnonuclear reactions involving stable and neutron-rich light nuclei has been created; it can be used in future for the study of various nuclear burning phenomena in different environments. Time-odd mean fields and their manifestations in terminating states, non-rotating and rotating nuclei have been studied in the framework of covariant density functional theory. Contrary to non-relativistic density functional theories these fields, which are important for a proper description of nuclear systems with broken time-reversal symmetry, are uniquely defined in the CDFT framework. Hyperdeformed nuclear shapes (with semi-axis ratio 2.5:1 and larger) have been studied in the Z = 40-58 part of nuclear chart. We strongly believe that such shapes could be studied experimentally in the future with full scale GRETA detector.

  7. Sextic potential for \\gamma -rigid prolate nuclei

    NASA Astrophysics Data System (ADS)

    Buganu, P.; Budaca, R.

    2015-10-01

    The equation of the Bohr-Mottelson Hamiltonian with a sextic oscillator potential is solved for γ -rigid prolate nuclei. The associated shape phase space is reduced to three variables which are exactly separated. The angular equation has the spherical harmonic functions as solutions, while the β equation is converted to the quasi-exactly solvable case of the sextic oscillator potential with a centrifugal barrier. The energies and the corresponding wave functions are given in closed form and depend, up to a scaling factor, on a single parameter. The {0}+ and {2}+ states are exactly determined, having an important role in the assignment of some ambiguous states for the experimental β bands. Due to the special properties of the sextic potential, the model can simulate, by varying the free parameter, a shape phase transition from a harmonic to an anharmonic prolate β -soft rotor crossing through a critical point. Numerical applications are performed for 39 nuclei: {}98-108Ru, {}{100,102}Mo, {}116-130Xe, {}{132,134}Ce, {}146-150Nd, {}{150,152}Sm, {}{152,154}Gd, {}{154,156}Dy, 172Os, {}180-196Pt, 190Hg and 222Ra. The best candidates for the critical point are found to be 104Ru and {}{120,126}Xe, followed closely by 128Xe, 172Os, 196Pt and 148Nd.

  8. A self-consistent study of triaxial black hole nuclei

    NASA Astrophysics Data System (ADS)

    Poon, Ming Yan

    Knowledge of the three-dimensional shapes of elliptical galaxies has not advanced much since the time of Edwin Hubble. Elliptical galaxies are still classified according to their luminosity distributions and the isophotal contour shapes of their two-dimensional images projected on the sky. Their intrinsic shapes could be oblate, prolate, or fully triaxial, since all such shapes produce perfectly elliptical contours on projection. One way to constrain the possible 3D shapes of elliptical galaxies is to attempt to construct self-consistent dynamical models with various shapes. In this study, models were constructed of the central regions (“nuclei”) of elliptical galaxies. Observed nuclei have a power-law dependence of stellar density on radius, and universally contain a single supermassive black hole at their center, with mass ˜106 109 M⊙ . At low energies in such nuclei, the motion was found to be essentially regular, i.e. non-chaotic; the gravitational potential can be considered as a perturbation to the integrable Keplerian potential. At higher energies, where the enclosed stellar mass is a few times the black hole mass, the black hole renders those orbits that come close to the black hole stochastic. This transition to global stochasticity is rapid and occurs at lower energies in more elongated nuclei. The self-consistency of triaxial models of black hole nuclei was demonstrated by using Schwarzschild's method to construct self-consistent orbital superpositions representing nuclei with different shapes. N-body integrations of Monte-Carlo realizations of the Schwarzschild solutions showed that some of these nuclei are stable; nearly prolate nuclei were found to be unstable, and they evolve rapidly to axisymmetric shapes. The possibility that nuclei may be triaxial in shape complicates the interpretation of stellar kinematical data from the centers of galaxies and may alter the inferred interaction rates between stars and supermassive black holes.

  9. Synthesis and study of atomic nuclei with Z > 100

    NASA Astrophysics Data System (ADS)

    Flerov, G. N.; Ter-Akopian, G. M.

    The studies of atomic nuclei with Z > 100 are closely related to the synthesis of new chemical elements and to the investigation of stability limits for the heaviest nuclides. From the mid-50s these studies have been carried out using intense heavy-ion beams and highly sensitive techniques designed for the physical and chemical identification of rare short-lived nuclei. The studies proceeded in two stages, the first one being characterized by the use of hot-fusion reactions between the U, Pu, Am, Cm and Cf target nuclei and the C, N, O, and Ne projectiles and the second being based on the use of the cold-fusion reactions induced by Cr, Mn, and Fe projectiles on Pb and Bi target nuclei. As a result, the chemical elements with atomic numbers from 102 to 109 have first been synthesized. The radioactive properties of over 40 isotopes of these elements have been investigated and unambiguous evidence has been obtained that shell effects play a decisive role for the stability of the Z ≳ 104 nuclei against spontaneous fission. This provides an experimental substantiation for the known hypothesis that the island of nuclear stability should lie around Z ⋍ 114 and N ⋍ 178 or 184. It has been proposed to synthesize elements with Z ≥ 110 by the complete fusion reactions of uranium and adjacent element nuclei with projectile nuclei such as Ar and Ca. The spontaneous fission of a product nucleus (a total of 26 events) has been observed in Dubna experiments with the 232Th + 44Ca and 236U + 40Ar reactions. The authors of those studies tentatively assigned this activity to the decay of the nuclei of element 110.

  10. Density distributions in nuclei

    NASA Astrophysics Data System (ADS)

    Strutinsky, V. M.; Magner, A. G.; Denisov, V. Yu.

    1985-03-01

    Density distribution across the nuclear surface is obtained in the approximation of relatively sharp nuclear edge. It is used to determine dynamical parts of the density relevant to density vibration resonances. Results of the simple calculations are in close agreement with detailed microscopic theories.

  11. Spin Modes in Nuclei and Nuclear Forces

    SciTech Connect

    Suzuki, Toshio; Otsuka, Takaharu

    2011-05-06

    Spin modes in stable and unstable exotic nuclei are studied and important roles of tensor and three-body forces on nuclear structure are discussed. New shell model Hamiltonians, which have proper tensor components, are shown to explain shell evolutions toward drip-lines and spin properties of both stable and exotic nuclei, for example, Gamow-Teller transitions in {sup 12}C and {sup 14}C and an anomalous M1 transition in {sup 17}C. The importance and the necessity of the repulsive monopole corrections in isospin T = 1 channel to the microscopic two-body interactions are pointed out. The corrections are shown to lead to the proper shell evolutions in neutron-rich isotopes. The three-body force, in particular the Fujita-Miyazawa force induced by {Delta} excitations, is pointed out to be responsible for the repulsive corrections among the valence neutrons. The important roles of the three-body force on the energies and transitions in exotic oxygen and calcium isotopes are demonstrated.

  12. Coulomb excitation of neutron-rich 138,140,142Xe at REX-ISOLDE

    NASA Astrophysics Data System (ADS)

    Kröll, Th.; Behrens, T.; Krücken, R.; Bildstein, V.; Gernhäuser, R.; Maierbeck, P.; Stefanescu, I.; Ivanov, O.; van de Walle, J.; Warr, N.; Butler, P. A.; Cederkäll, J.; Delahaye, P.; Fraile, L. M.; Georgiev, G.; Köster, U.; Sieber, T.; Voulot, D.; Wenander, F.; Kent, P. E.; Ekström, A.; Speidel, K.-H.; Leske, J.; Schielke, S.; Habs, D.; Lutter, R.; Thirolf, P.; Scheit, H.; Davinson, T.

    2007-11-01

    We report on “safe” Coulomb excitation of neutron-rich 138,140,142Xe nuclei. The radioactive nuclei have been produced by ISOLDE at CERN and post-accelerated by the REX-ISOLDE facility. The γ-rays emitted by the decay of excited states have been detected by the MINIBALL array. Recent results are presented.

  13. [Closing diastemas].

    PubMed

    Vieira, L C; Pereira, J C; Coradazzi, J L; Francischone, C E

    1990-01-01

    The authors describe a clinical case of closing upper central incisives diastema, reconstructiva of a conoid upper lateral and the rechaping of an upper canine to a lateral incisive. The material used was composite resin.

  14. The morphology of cometary nuclei

    NASA Astrophysics Data System (ADS)

    Keller, H. U.; Jorda, L.

    the planetary system (4.5 Gy). Therefore, observed comets could only recently have arrived on their orbits dipping inside the inner Solar System. This reservoir of comets must have been established during the formation process of the planetary system itself. Cometesimals were agglomerated from interstellar/interplanetary gas and dust and scattered out of the inner Solar System by the giant outer planets (Section 2.3). This scheme implies that a central part of a comet, its nucleus, is stable enough to survive these perturbations. It must also be stable enough to pass the vicinity of the sun for many times in the case of a short-period comet. Comets are bright and large when they are close to the sun and fade quickly when they recede beyond about 2AU. Only with the advent of photography and large astronomical telescopes could a comet be followed until it becomes a starlike point source. What makes comets active near the Sun, blowing their appearances up to the order of 105 km? Bright comets often develop tails two orders of magnitude longer. In an attempt to explain the cometary appearance, Bredichin (1903) introduced a mechanical model where repulsive forces drive the particles away from a central condensation. Spectroscopy revealed that dust grains reflect the solar irradiation. In addition, simple molecules, radicals and ions were found as constituents of the cometary coma and tail. The nature of the central condensation remained mysterious for a long time because of the observational dilemma. When the comet is close to the Earth and therefore to the Sun the dense coma obscures the view into its centre. When activity recedes the comet is too far away and too dim for detailed observations of its central condensation. During the middle of the nineteenth century the connection between comets and meteor streams was established. Schiaparelli (1866) calculated the dispersion of cometary dust within the orbital plane. From this time on the perception that the central

  15. New results on the structure of exotic nuclei

    NASA Astrophysics Data System (ADS)

    Sakurai, Hiroyoshi

    2015-04-01

    `Exotic nuclei' far from the stability line are unique objects of many-body quantum system, where ratios of neutron number to proton number are much larger or much smaller than those of nuclei found in nature. Their exotic properties and phenomena emerge from their large isospin asymmetry, and even affect scenarios of nucleosynthesis in universe. One of the exotic emergences is shell evolution. The magic numbers of stable nuclei are known; 2, 8, 20, 28, 50, 82 and 126. However the numbers 8, 20 and 28 have been found no more magic in a neutron-rich region, and new magic numbers such as 6, 16, 32 and 34 have been discovered. To access nuclei far from the stability line, especially neutron-rich nuclei, a large heavy-ion accelerator facility `Radioactive Isotope Beam Factory (RIBF)' was constructed at RIKEN, Japan in 2007. The facility is highly optimized for inflight production of fission fragments via a U beam. The accelerator complex delivers an intense 345 MeV/u U beam. The U nuclide is converted at a target to fission fragments. The fragments of interest are collected and separated at an inflight separator, and are delivered to several experimental devices. The shell evolution programs at RIBF have been conducted with two methods; in-beam gamma spectroscopy and decay spectroscopy. A standard setup of in-beam gamma spectroscopy is combination of a NaI gamma detector array `DALI2' and a beam line spectrometer `ZeroDegree Spectrometer (ZDS)'. Coincidence measurements of de-excitation gamma rays at DALI2 and of reaction products at ZDS make it possible to select reaction channels event-by-event and to observe excited states of exotic nuclei in a specific reaction channel. Recently, a French-made thick liquid hydrogen target system `MINOS' has been introduced to access more neutron-rich nuclei. Isomer and beta-delayed gamma spectroscopy is organized with a Euroball germanium cluster array system `EURICA' and an active silicon stopper In this talk, I would like to

  16. Generalized parton distributions in nuclei

    SciTech Connect

    Vadim Guzey

    2009-12-01

    Generalized parton distributions (GPDs) of nuclei describe the distribution of quarks and gluons in nuclei probed in hard exclusive reactions, such as e.g. deeply virtual Compton scattering (DVCS). Nuclear GPDs and nuclear DVCS allow us to study new aspects of many traditional nuclear effects (nuclear shadowing, EMC effect, medium modifications of the bound nucleons) as well as to access novel nuclear effects. In my talk, I review recent theoretical progress in the area of nuclear GPDs.

  17. Electroweak properties of light nuclei

    NASA Astrophysics Data System (ADS)

    Pastore, Saori

    2016-03-01

    In this talk, I will review the present understanding of nuclear electroweak properties of light nuclei, including electromagnetic moments, form factors and transitions, as well as selected beta decays in A <= 10 nuclei. Emphasis will be on calculations based on nuclear Hamiltonians that include two- and three-nucleon realistic potentials, along with one- and two-body electroweak currents. Work supported by the U.S. DOE, Office of Nuclear Physics, under contract DE-AC52-06NA25396.

  18. The nature of comet nuclei

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.; Walker, Russell G.

    1992-01-01

    The icy-conglomerate model of comet nuclei has dominated all others since its introduction. It provided a basis for understanding the non-gravitational motions of comets which had perplexed dynamicists up to that time, and provided a focus for understanding cometary composition and origin. The image of comets as dirty snowballs was quickly adopted. Comet nuclei including their trail mass loss rates and refractory to volatile mass ratios are described.

  19. Properties and synthesis of heavy nuclei and properties of neutron star matter

    NASA Technical Reports Server (NTRS)

    Buchler, J. R.

    1974-01-01

    The nuclear Thomas-Fermi model which is based on nuclear matter calculations has been successfully applied to the study of the bulk properties of nuclei. It is ideally suited for extrapolation into the region of very neutron-rich and of superheavy nuclei. It is therefore a valuable approach for r-process calculations as well as for the study of neutron star matter at subnuclear densities.

  20. Beta decay asymmetry in mirror nuclei: A=9

    SciTech Connect

    Tengblad, Olof; Borge, M. J. G.; Fraile, L. M.; Axelsson, L.; Jonson, B.; Nyman, G.; Markenroth, K.; Wenander, F.; Bergmann, U.; Fynbo, H. O. U.; Hornshoej, P.; Mukha, I.; Riisager, K.; Jading, Y.; Nilsson, T.; Martel, I.; Rolander, K. Wilhelmsen

    1999-11-16

    Investigations of light nuclei close to the drip lines have revealed new and intriguing features of the nuclear structure. The occurrence of halo structures in loosely bound systems has had a great impact on the nuclear physics research in the last years, as intriguing, but not yet solved, is the nature of transitions with very large beta strength. We report here on the investigation of this latter feature by an accurate measurement of the beta decay asymmetry between the mirror nuclei in the A=9 mass chain.

  1. Beta Decay Asymmetry in Mirror Nuclei: A = 9.

    SciTech Connect

    Olof Tengblad; L. Axelsson; U. Bergmann; M.J.G. Borge; L.M. Fraile; H.O.U. Fynbo; P. Hornshoj; Y. Jading; B. Jonson; T. Nilsson; G. Nyman; K. Markenroth; I. Martel; I. Mukha; K. Riisager; F. Wenander; K. Wilhelmsen Rolander

    1999-12-31

    Investigations of light nuclei close to the drip lines have revealed new and intriguing features of the nuclear structure. The occurrence of halo structures in loosely bound systems has had a great impact on the nuclear physics research in the last years, as intriguing, but not yet solved, is the nature of transitions with very large beta strength. We report here on the investigation of this latter feature by an accurate measurement of the beta decay asymmetry between the mirror nuclei in the A = 9 mass chain.

  2. Deformations and Quasiparticle Spectra of Nuclei in the Nobelium Region

    NASA Astrophysics Data System (ADS)

    Shi, Yue; Dobaczewski, J.; Greenlees, P. T.; Toivanen, J.; Toivanen, P.

    2014-09-01

    We have performed self-consistent Skyrme Hartree-Fock-Bogolyubov calculations for nuclei close to 254No. Self-consistent deformations, including β2,4,6,8 as functions of the rotational frequency, were determined for even-even nuclei 246,248,250Fm, 252,254No, and 256Rf. The quasiparticle spectra for N = 151 isotones and Z = 99 isotopes were calculated and compared with experimental data and the results of Woods-Saxon calculations. We found that our calculations give high-order deformations similar to those obtained for the Woods-Saxon potential, and that the experimental quasiparticle energies are reasonably well reproduced.

  3. Superheavy Nuclei: Which Regions of Nuclear Map are Accessible for the Nearest Studies

    NASA Astrophysics Data System (ADS)

    Karpov, A. V.; Zagrebaev, V. I.; Greiner, W.

    2015-11-01

    Use of fusion reactions for synthesis and studying new superheavy nuclei is considered in the paper. Perspectives of synthesis of new elements with Z > 118 are discussed. The gap of unknown SH nuclei, located between the isotopes which were produced earlier in the cold and hot fusion reactions, can be filled in fusion reactions of 48Ca with available lighter isotopes of Pu, Am, and Cm. Cross sections for the production of these nuclei are predicted to be rather large. The found area of β+-decaying SH nuclei with 111 ≤ Z ≤ 115 located to the "right" (more neutron-rich) to those synthesized recently in Dubna in 48Ca-induced fusion reactions gives a unique chance to synthesize in fusion reactions the most stable SH nuclei located at the center of the island of stability.

  4. Fission Study of Actinide Nuclei Using Multi-nucleon Transfer Reactions

    NASA Astrophysics Data System (ADS)

    Nishio, Katsuhisa; Hirose, Kentaro; Léguillon, R.; Makii, Hiroyuki; Nishinaka, Ichiro; Orlandi, Riccardo; Smallcombe, James; Tsukada, Kazuaki; Chiba, Satoshi; Ohtsuki, Tsutomu; Tatsuzawa, Ryotaro; Takaki, Naoyuki

    We have developed a set up to measure fission properties of excited compound nuclei populated by multi-nucleon transfer reactions. This approach has an advantage that we can study fission of neutron-rich nuclei which cannot be accessed by particle or charged-particle capture reactions. Unique feature in our setup is that we can produce fission data for many nuclei depending on different transfer channels. Also wide excitation energy range can be covered in this set up, allowing us to measure the excitation energy dependence of the fission properties. Preliminary data obtained in the 18O + 238U reaction will be presented.

  5. New dimensions of the periodic system: superheavy, superneutronic, superstrange, antimatter nuclei

    NASA Astrophysics Data System (ADS)

    Greiner, Walter

    2010-12-01

    The possibilities for the extension of the periodic system into the islands of superheavy (SH) elements, to and beyond the neutron drip line and to the sectors of strangeness and antimatter are discussed. The multi-nucleon transfer processes in low-energy damped collisions of heavy actinide nuclei may help us to fill the gap between the nuclei produced in the "hot" fusion reactions and the continent of known nuclei. In these reactions we may also investigate the "island of stability". In many such collisions the lifetime of the composite giant system consisting of two touching nuclei turns out to be rather long (≥10-20 s); sufficient for observing line structure in spontaneous positron emission from super-strong electric fields (vacuum decay), a fundamental QED process not observed yet experimentally. At the neutron-rich sector near the drip line islands and extended ridges of quasistable nuclei are predicted by HF calculations. Such nuclei, as well as very long living superheavy nuclei may be provided in double atomic bomb explosions. A tremendously rich scenario of new nuclear structure emerges with new magic numbers in the strangeness domain. Various production mechanisms are discussed for these objects and for antinuclei in high energy heavy-ion collisions.

  6. New dimensions of the periodic system: superheavy, superneutronic, superstrange, antimatter nuclei

    SciTech Connect

    Greiner, Walter

    2010-12-23

    The possibilities for the extension of the periodic system into the islands of superheavy (SH) elements, to and beyond the neutron drip line and to the sectors of strangeness and antimatter are discussed. The multi-nucleon transfer processes in low-energy damped collisions of heavy actinide nuclei may help us to fill the gap between the nuclei produced in the ''hot'' fusion reactions and the continent of known nuclei. In these reactions we may also investigate the ''island of stability''. In many such collisions the lifetime of the composite giant system consisting of two touching nuclei turns out to be rather long ({>=}10{sup -20} s); sufficient for observing line structure in spontaneous positron emission from super-strong electric fields (vacuum decay), a fundamental QED process not observed yet experimentally. At the neutron-rich sector near the drip line islands and extended ridges of quasistable nuclei are predicted by HF calculations. Such nuclei, as well as very long living superheavy nuclei may be provided in double atomic bomb explosions. A tremendously rich scenario of new nuclear structure emerges with new magic numbers in the strangeness domain. Various production mechanisms are discussed for these objects and for antinuclei in high energy heavy-ion collisions.

  7. Cloud Condensation Nuclei Measurements in Tropical Cyclones

    NASA Technical Reports Server (NTRS)

    Hudson, J. G.; Simpson, J.

    2002-01-01

    The first measurements of cloud condensation nuclei (CCN) within and around tropical cyclones were made with the Desert Research Institute (DRI) CCN spectrometer (Hudson 1909) from a NOAA P-3 Hurricane Hunter aircraft throughout the 2001 season. Two penetrations of the closed eye of Hurricane Erin off the northeast US coast on Sept. 10 showed concentrations consistently well in excess of 1000 per cubic cm at approximately 1.4% supersaturation. Simultaneous condensation nuclei (CN--total particle) concentrations were consistently well in excess of 2000 per cubic cm throughout these closed eye penetrations. These within eye measurements at 4 km altitude for exceeded CCN and CN measurements just outside of the storm at similar altitudes--300 and 600 per cubic cm respectively. These CCN and CN concentrations within this closed eye were far above concentrations in maritime air masses; they are characteristic of continental or polluted air masses. Although there was a possibility that Saharan duct may have gotten into this storm these sub tenth micrometer particles are much too small and much too numerous to be dust. Such high concentrations may have originated from European air pollution, which may have been transported by similar airflow patterns to those that carry Saharan dust across the Atlantic. These high concentrations may be a manifestation of descending air that brings higher concentrations that are often characteristic of the upper troposphere (Clarke and Kapustin 2002). Later in the month measurements in Humberto showed highly variable CCN and CN concentrations that ranged from lots than 5 per cubic cm to more than 1000 per Cubic cm over km scale distances within and around the open eye of this tropical storm/hurricane. These very low concentrations suggest strong cloud scavenging.

  8. Segmentation of touching cell nuclei using gradient flow tracking.

    PubMed

    Li, G; Liu, T; Nie, J; Guo, L; Chen, J; Zhu, J; Xia, W; Mara, A; Holley, S; Wong, S T C

    2008-07-01

    Reliable cell nuclei segmentation is an important yet unresolved problem in biological imaging studies. This paper presents a novel computerized method for robust cell nuclei segmentation based on gradient flow tracking. This method is composed of three key steps: (1) generate a diffused gradient vector flow field; (2) perform a gradient flow tracking procedure to attract points to the basin of a sink; and (3) separate the image into small regions, each containing one nucleus and nearby peripheral background, and perform local adaptive thresholding in each small region to extract the cell nucleus from the background. To show the generality of the proposed method, we report the validation and experimental results using microscopic image data sets from three research labs, with both over-segmentation and under-segmentation rates below 3%. In particular, this method is able to segment closely juxtaposed or clustered cell nuclei, with high sensitivity and specificity in different situations.

  9. Dribs II:. a Source of Radioactive Nuclei

    NASA Astrophysics Data System (ADS)

    Szöllős, O.; Kliman, J.; Oganessian, Yu. Ts.; Itkis, M. G.; Dmitriev, S. N.; Mishinsky, G. V.; Zhemenik, V. I.

    2002-12-01

    The facility for neutron-rich nuclei production, as a specific part of the project DRIBS - phase II, based on the use of photofission and the characteristics of microtron MT-25 as a source of bremsstrahlung photons are described. Target selection with regard to maximum yield production of strong neutron-rich fission products and with respect to its safety and availability is discussed. Geant 4 simulation toolkit was used to obtain bremsstrahlung γ-beam characteristics and its angular spred was compared with measurements on MT-25 microtron. Next, calculation of fission-rate and fission density in 238U target at nominal values of MT-25 microtron are presented. Calculations of the yield from photofission based on the Wahl's ZP model for charge distribution of fission fragments are compared with experimental data for independent yield of xenon isotopes measured. As result the independent and cummulative yields from photofission of 238U for mictrotron MT-25, as a driver accelerator for DRIBS II, for up to 890 isotopes and their isomers were obtained. Mean characteristics of this compact facility with some others RIB projects are compared.

  10. Cavitation inception from bubble nuclei

    PubMed Central

    Mørch, K. A.

    2015-01-01

    The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure–time history of the water. A recent model and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes. PMID:26442138

  11. Geomagnetically trapped energetic helium nuclei

    SciTech Connect

    Chen, J.; Gregory Guzik, T.; Wefel, J.P.; Roger Pyle, K.; Cooper, J.F.

    1996-07-01

    Geomagnetically trapped helium nuclei, at high energy ({approximately}40{endash}100 MeV/nucleon), have been measured by the ONR-604 instrument during the 1990/1991 CRRES mission. The ONR-604 instrument resolved the isotopes of helium with a mass resolution of 0.1 amu. The energetic helium observed at {ital L}{lt}2.3 have a pitch angle distribution peaking perpendicular to the local magnetic field, which is characteristic of a trapped population. Both the trapped {sup 3}He and {sup 4}He show two peaks at {ital L}=1.2 and 1.9. Each isotope{close_quote}s flux, in each peak, can be characterized by a power law energy spectrum. The energy spectrum of the {sup 3}He is different from that of {sup 4}He, indicating that the {sup 3}He/{sup 4}He ratio is energy dependent. Over the energy range of 51{endash}86 MeV/nucleon, the {sup 3}He/{sup 4}He ratio is 8.7{plus_minus}3.1 at {ital L}=1.1{endash}1.5 and is 2.4{plus_minus}0.6 at {ital L}=1.5{endash}2.3. The trapped helium counting rates decrease gradually with time during the CRRES mission, when the anomalous component is excluded from the inner heliosphere, indicating that these high energy ions were not injected by flares during this time period. The decrease in intensity is attributed mainly to the events around {ital L}=1.9. The helium around {ital L}=1.2, dominated by {sup 3}He, does not show a significant temporal evolution, which implies a long-term energetic trapped {sup 3}He population. Two possible origins of the geomagnetically trapped helium isotopes are the interactions of energetic protons with the upper atmosphere and/or the inward diffusion and acceleration of helium ions due to electric-field fluctuations. {copyright} {ital 1996 American Institute of Physics.}

  12. STELLAR TRANSITS IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Beky, Bence; Kocsis, Bence E-mail: bkocsis@cfa.harvard.edu

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 10{sup 6} solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or {approx}10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  13. Stellar Transits in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Béky, Bence; Kocsis, Bence

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 106 solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or ~10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  14. Polarized EMC Effect in Nuclei

    SciTech Connect

    Ian Cloet; A. W. Thomas; W. Bentz

    2006-06-05

    The discovery of the EMC effect and the proton spin crisis by the European Muon Collaboration are two of the standout experiments of the last 25 years. It is therefore surprising that there has been no experimental and little theoretical investigation of the spin structure functions of atomic nuclei. To address this we present results for the spin-dependent structure functions of nuclei. The quark degrees of freedom in nuclei are accessed via the convolution formalism. Where the nucleon bound state is obtained by solving the relativistic Faddeev equation, and a relativistic shell model is used to model the atomic nucleus. We find the important result that the medium modifications to the polarized structure functions are about twice that of the unpolarized case.

  15. Medium-spin states of the neutron-rich 87,89Br isotopes: configurations and shapes

    NASA Astrophysics Data System (ADS)

    Nyakó, B. M.; Timár, J.; Csatlós, M.; Dombrádi, Zs; Krasznahorkay, A.; Kuti, I.; Sohler, D.; Tornyi, T. G.; Czerwiński, M.; Rząca-Urban, T.; Urban, W.; Bączyk, P.; Atanasova, L.; Balabanski, D. L.; Sieja, K.; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; de France, G.; Simpson, G. S.; Ur, C. A.

    2016-06-01

    Medium-spin excited states of the neutron-rich 87Br and 89Br nuclei were observed and studied for the first time. They were populated in fission of 235U induced by the cold-neutron beam of the PF1B facility of the Institut Laue-Langevin, Grenoble. The measurement of γ radiation following fission has been performed using the EXILL array of Ge detectors. The observed level schemes were compared with results of large valence space shell model calculations. Both medium-spin level schemes consist of band-like structures, which can be understood as bands built on the πf 5/2, πp 3/2 and πg 9/2 configurations. Both nuclei have 5/2- ground state spin-parity contrary to the odd-mass Br isotopes containing fewer neutrons, which have 3/2- ground state spin-parity. On the basis of the properties of the πg 9/2 decoupled bands the deformations of the 87Br and 89Br fit to the systematics of nuclei in the region. 87Br is close to the vibrational limit, while 89Br is more rotational.

  16. Medium-spin states of the neutron-rich 87,89Br isotopes: configurations and shapes

    NASA Astrophysics Data System (ADS)

    Nyakó, B. M.; Timár, J.; Csatlós, M.; Dombrádi, Zs; Krasznahorkay, A.; Kuti, I.; Sohler, D.; Tornyi, T. G.; Czerwiński, M.; Rząca-Urban, T.; Urban, W.; Bączyk, P.; Atanasova, L.; Balabanski, D. L.; Sieja, K.; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; de France, G.; Simpson, G. S.; Ur, C. A.

    2016-06-01

    Medium-spin excited states of the neutron-rich 87Br and 89Br nuclei were observed and studied for the first time. They were populated in fission of 235U induced by the cold-neutron beam of the PF1B facility of the Institut Laue-Langevin, Grenoble. The measurement of γ radiation following fission has been performed using the EXILL array of Ge detectors. The observed level schemes were compared with results of large valence space shell model calculations. Both medium-spin level schemes consist of band-like structures, which can be understood as bands built on the πf 5/2, πp 3/2 and πg 9/2 configurations. Both nuclei have 5/2‑ ground state spin-parity contrary to the odd-mass Br isotopes containing fewer neutrons, which have 3/2‑ ground state spin-parity. On the basis of the properties of the πg 9/2 decoupled bands the deformations of the 87Br and 89Br fit to the systematics of nuclei in the region. 87Br is close to the vibrational limit, while 89Br is more rotational.

  17. Octupole shapes in heavy nuclei

    SciTech Connect

    Ahmad, I.

    1994-08-01

    Theoretical calculations and measurements show the presence of strong octupole correlations in thecyround states and low-lying states of odd-mass and odd-odd nuclei in the RaPa region. Evidence for octupole correlations is provided by the observation of parity doublets and reductions in M1 matrix elements, decoupling parameters, and Coriolis matrix elements Involving high-j states. Enhancement of E1 transition rates has also been observed for some of the octupole deformed nuclei. The most convincing argument for octupole deformation is provided by the similarities of the reduced alpha decay rates to the two members of parity doublets.

  18. Cloud condensation nuclei near marine cumulus

    NASA Technical Reports Server (NTRS)

    Hudson, James G.

    1993-01-01

    Extensive airborne measurements of cloud condensation nucleus (CCN) spectra and condensation nuclei below, in, between, and above the cumulus clouds near Hawaii point to important aerosol-cloud interactions. Consistent particle concentrations of 200/cu cm were found above the marine boundary layer and within the noncloudy marine boundary layer. Lower and more variable CCN concentrations within the cloudy boundary layer, especially very close to the clouds, appear to be a result of cloud scavenging processes. Gravitational coagulation of cloud droplets may be the principal cause of this difference in the vertical distribution of CCN. The results suggest a reservoir of CCN in the free troposphere which can act as a source for the marine boundary layer.

  19. Exotic nuclei and nuclear forces

    NASA Astrophysics Data System (ADS)

    Otsuka, Takaharu

    2013-01-01

    I overview new aspects of the structure of exotic nuclei as compared to stable nuclei, focusing on several characteristic effects of nuclear forces. The shell structure of nuclei has been proposed by Mayer and Jensen, and has been considered to be kept valid basically for all nuclei, with well-known magic numbers, 2, 8, 20, 28, 50, …. Nuclear forces were shown, very recently, to change this paradigm. It will be presented that the evolution of shell structure occurs in various ways as more neutrons and/or protons are added, and I will present basic points of this shell evolution in terms of the monopole interaction of nuclear forces. I will discuss three types of nuclear forces. The first one is the tensor force. The tensor force is one of the most fundamental nuclear forces, but its first-order effect on the shell structure has been clarified only recently in studies on exotic nuclei. The tensor force can change the spin-orbit splitting depending on the occupation of specific orbits. This results in changes of the shell structure in many nuclei, and consequently some of Mayer-Jensen's magic numbers are lost and new ones emerge, in certain nuclei. This mechanism can be understood in an intuitive way, meaning that the effect is general and robust. The second type of nuclear forces is central force. I will show a general but unknown property of the central force in the shell-model Hamiltonian that can describe nuclear properties in a good agreement with experiment. I will then demonstrate how it can be incorporated into a simple model of the central force, and will discuss how this force works in the shell evolution. Actually, by combining this central force with the tensor force, one can understand and foresee how the same proton-neutron interaction drives the shell evolution, for examples such as Sn/Sb isotopes, N = 20 nuclei and Ni/Cu isotopes. The distribution of single-particle strength is discussed also in comparison to (e,e‧p) experiment on 48Ca. The shell

  20. Dynamical effects in fusion with exotic nuclei

    NASA Astrophysics Data System (ADS)

    Vo-Phuoc, K.; Simenel, C.; Simpson, E. C.

    2016-08-01

    Background: Reactions with stable beams have demonstrated strong interplay between nuclear structure and fusion. Exotic beam facilities open new perspectives to understand the impact of neutron skin, large isospin, and weak binding energies on fusion. Microscopic theories of fusion are required to guide future experiments. Purpose: To investigate new effects of exotic structures and dynamics in near-barrier fusion with exotic nuclei. Method: Microscopic approaches based on the Hartree-Fock (HF) mean-field theory are used for studying fusion barriers in -54Ca40+116Sn reactions for even isotopes. Bare potential barriers are obtained assuming frozen HF ground-state densities. Dynamical effects on the barrier are accounted for in time-dependent Hartree-Fock (TDHF) calculations of the collisions. Vibrational couplings are studied in the coupled-channel framework and near-barrier nucleon transfer is investigated with TDHF calculations. Results: The development of a neutron skin in exotic calcium isotopes strongly lowers the bare potential barrier. However, this static effect is not apparent when dynamical effects are included. On the contrary, a fusion hindrance is observed in TDHF calculations with the most neutron-rich calcium isotopes which cannot be explained by vibrational couplings. Transfer reactions are also important in these systems due to charge equilibration processes. Conclusions: Despite its impact on the bare potential, the neutron skin is not seen as playing an important role in the fusion dynamics. However, the charge transfer with exotic projectiles could lead to an increase of the Coulomb repulsion between the fragments, suppressing fusion. The effects of transfer and dissipative mechanisms on fusion with exotic nuclei deserve further studies.

  1. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-01-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  2. Proton Distribution in Heavy Nuclei

    DOE R&D Accomplishments Database

    Johnson, M. H; Teller, E.

    1953-11-13

    It is reasoned that, from considerations connected with beta-decay stability and Coulomb repulsion forces, a neutron excess is developed on the surface of heavy nuclei. Several consequences of this qualitative analysis in nucleon interactions are briefly noted. (K.S.)

  3. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-08-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  4. Nuclei and propeller cavitation inception

    SciTech Connect

    Gindroz, B.; Billet, M.L.

    1994-12-31

    Propeller cavitation inception tests were conducted in the Grand Tunnel Hydrodynamique (GTH) of the Bassin d`Essaid des Carenes. Both acoustic and visual cavitation inception were determined for leading-edge sheet, travelling bubble, and tip vortex. These data were obtained for specific water quality conditions. The water quality was determined from cavitation susceptibility meter measurements for degassed water (maximum liquid tension, few nuclei), low injection rate of microbubbles (medium liquid tension, low nuclei concentration), medium injection rate of microbubbles (medium liquid tension, high nuclei concentration) and high injection rate of microbubbles (minimum liquid tension, high nuclei concentration). Results clearly demonstrate a different influence of water quality for each type of cavitation. Little variation in cavitation inception index for a significant increase in liquid tension and microbubble size distribution was found for leading-edge sheet; however, tip vortex cavitation inception index decreased significantly for an increase in liquid tension. In addition, a dependency on event rate was determined for tip vortex cavitation inception.

  5. Transitional nuclei near shell closures

    SciTech Connect

    Mukherjee, G.

    2014-08-14

    High spin states in Bismuth and Thallium nuclei near the Z = 82 shell closure and Cesium nuclei near the N = 82 shell closure in A = 190 and A = 130 regions, respectively, have been experimentally investigated using heavy-ion fusion evaporation reaction and by detecting the gamma rays using the Indian National Gamma Array (INGA). Interesting shape properties in these transitional nuclei have been observed. The results were compared with the neighboring nuclei in these two regions. The total Routhian surface (TRS) calculations have been performed for a better understanding of the observed properties. In mass region A = 190, a change in shape from spherical to deformed has been observd around neutron number N = 112 for the Bi (Z = 83) isotopes with proton number above the magic gap Z = 82, whereas, the shape of Tl (Z = 81) isotopes with proton number below the magic gap Z = 82 remains stable as a function of neutron number. An important transition from aplanar to planar configuration of angular momentum vectors leading to the occurance of nuclar chirality and magnetic rotation, respectively, has been proposed for the unique parity πh{sub 11/2}⊗νh{sub 11/2} configuration in Cs isotopes in the mass region A ∼ 130 around neutron number N = 79. These results are in commensurate with the TRS calculations.

  6. Electromagnetic structure of light nuclei

    DOE PAGES

    Pastore, Saori

    2016-03-25

    Here, the present understanding of nuclear electromagnetic properties including electromagnetic moments, form factors and transitions in nuclei with A ≤ 10 is reviewed. Emphasis is on calculations based on nuclear Hamiltonians that include two- and three-nucleon realistic potentials, along with one- and two-body electromagnetic currents derived from a chiral effective field theory with pions and nucleons.

  7. International Symposium on Exotic Nuclei

    NASA Astrophysics Data System (ADS)

    Penionzhkevich, Yu. E.; Cherepanov, E. A.

    Methods of production of light exotic nuclei and study of their ptoperties -- Superheavy elements. Syhnthesis and properties -- Nuclear fission -- Nuclear reactions -- rare processes, decay and nuclear structure -- Experimental set-ups and future projects -- Radioactive beams. Production and research programmes -- Public relations.

  8. Expectations and Limits to Synthesize Nuclei with Z ≥ 120

    NASA Astrophysics Data System (ADS)

    Giardina, G.; Fazio, G.; Mandaglio, G.; Manganaro, M.; Nasirov, A. K.; Romaniuk, M. V.; Saccà, C.

    In order to explore the possibilities to synthesize the new superheavy elements with Z=120, 122, 124, 126 some hot-fusion (mass asymmetric) reactions and cold-fusion (less mass asymmetric) reactions are studied. The dynamics of reaction with massive nuclei and the formation probability of heavy and superheavy elements with Z=90-126 in the asymmetric and symmetric reactions are discussed. The systematics of fusion probability PCN and evaporation residue cross section σER in these reactions are presented. Moreover, we explore the possibility of synthesis of superheavy nuclei by the use of reaction with the neutron rich radioactive beam 132Sn, and by symmetric reactions like 136Xe+136Xe and 139,149La+ 139,149La.

  9. Probing the Evolution of the Shell Structures in Exotic Nuclei

    SciTech Connect

    De Angelis, Giacomo

    2008-11-11

    Magic numbers are a key feature in finite Fermion systems since they are strongly related to the underlying mean field. The size of the shell gaps and their evolution far from stability can be linked to the shape and symmetry of the nuclear mean field. Moreover the study of nuclei with large neutron/proton ratio allow to probe the density dependence of the effective interaction. Changes of the nuclear density and size in nuclei with increasing N/Z ratios are expected to lead to different nuclear symmetries and excitations. In this contribution I will discuss some selected examples which show the big potential of stable beams and of binary reactions for the study of the properties of the neutron-rich nuclear many body systems.

  10. Adaptive segmentation of nuclei in H&S stained tendon microscopy

    NASA Astrophysics Data System (ADS)

    Chuang, Bo-I.; Wu, Po-Ting; Hsu, Jian-Han; Jou, I.-Ming; Su, Fong-Chin; Sun, Yung-Nien

    2015-12-01

    Tendiopathy is a popular clinical issue in recent years. In most cases like trigger finger or tennis elbow, the pathology change can be observed under H and E stained tendon microscopy. However, the qualitative analysis is too subjective and thus the results heavily depend on the observers. We develop an automatic segmentation procedure which segments and counts the nuclei in H and E stained tendon microscopy fast and precisely. This procedure first determines the complexity of images and then segments the nuclei from the image. For the complex images, the proposed method adopts sampling-based thresholding to segment the nuclei. While for the simple images, the Laplacian-based thresholding is employed to re-segment the nuclei more accurately. In the experiments, the proposed method is compared with the experts outlined results. The nuclei number of proposed method is closed to the experts counted, and the processing time of proposed method is much faster than the experts'.

  11. Isotopic dependence of induced fission cross sections for heavy nuclei

    NASA Astrophysics Data System (ADS)

    Zubov, A. S.; Bolgova, O. N.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2009-10-01

    Using the statistical model, we calculate the induced fission cross sections for the nuclei 211-223Ra in their peripheral collisions with 208Pb. The role of closed shell N = 126 is studied. Level densities of the Fermi-gas model and of the model with collective enhancement are used. Taking into account the particle-hole excitation in addition to the collective Coulomb excitation, we obtain satisfactory agreement with the experimental data.

  12. Production of actinide nuclei by multi-nucleon transfer

    SciTech Connect

    Lauritsen, T.; Ahmad, I.; Carpenter, M.P.

    1995-08-01

    Multi-nucleon transfers have increasingly allowed us to reach parts of the nuclear chart where regular compound nuclear reactions are prohibited. The interesting region of Ra and Rn, where a rich tapestry of nuclear structure manifests itself, is now accessible using this technique of deep inelastic scattering. In particular, these nuclei are predicted to lie at the onset of octupole deformation and the region is rich in examples of shape coexistence. There are several theoretical predictions of nuclear structure of these nuclei that have not been experimentally tested. Moreover, there is serious disagreement among these theories. We used a beam of {sup 136}Xe at 720 MeV from ATLAS on a target of {sup 232}Th to produce a range of Rn isotopes, with a mass from 220 to 224, and Ra isotopes with masses greater than 222. The beam energy, target and beam were selected carefully to enhance the cross-section for production of these nuclei and reduce the Doppler broadening of the gamma rays that were observed in the Argonne Notre Dame gamma-ray facility. The 12 germanium detectors of this array allowed the observation of gamma-gamma coincidences. The inner ball of 50 BGO detectors allowed us to record the multiplicity and sum-energy information for each event. The latter should permit us to determine the entry region in the products of the transfer reaction. We had four successful days of beam-time, when we collected in excess of 8 x 10{sup 7} events. Data analysis is in progress at the University of Liverpool. A complete set of spectroscopic information on the yrast structure of the many nuclei produced in this reaction is being extracted.

  13. Evaporation Residue Yields in Reactions of Heavy Neutron-Rich Radioactive Ion Beams with 64Ni and 96Zr Targets

    SciTech Connect

    Shapira, Dan; Liang, J Felix; Gross, Carl J; Varner Jr, Robert L; Beene, James R; Stracener, Daniel W; Mueller, Paul Edward; Kolata, Jim J; Roberts, Amy; Loveland, Walter; Vinodkumar, A. M.; Prisbrey, Landon; Sprunger, Peter H; Grzywacz-Jones, Kate L; Caraley, Anne L

    2009-01-01

    As hindrance sets in for the fusion of heavier systems, the effect of large neutron excess in the colliding nuclei on their probability to fuse is still an open question. The detection of evaporation residues (ERs), however, provides indisputable evidence for the fusion (complete and incomplete) in the reaction. We therefore devised a system with which we could measure ERs using low intensity neutron-rich radioactive ion beams with an efficiency close to 100%. We report on measurements of the production of ERs in collisions of {sup 132,134}Sn, {sup 134}Te and {sup 134}Sb ion beams with medium mass, neutron-rich targets. The data taken with {sup 132,134}Sn bombarding a {sup 64}Ni target are compared to available data (ERs and fusion) taken with stable Sn isotopes. Preliminary data on the fusion of {sup 132}Sn with {sup 96}Zr target are also presented.

  14. Neutron-rich B isotopes studied with antisymmetrized molecular dynamics

    SciTech Connect

    Kanada-En`yo, Y.; Horiuchi, H.

    1995-08-01

    Structure of odd-even B isotopes up to the neutron dripline is studied systematically with the antisymmetrized molecular dynamics (AMD). The AMD method has already proved to be a powerful theoretical approach for the systematic study of nuclear structure in extensive region including exotic neutron-rich nuclei as well as ordinary nuclei. It is owing to its flexible nature free from any model assumptions such as the existence of clusters. The energies and other observed data of B isotopes are reproduced well. Especially very good reproduction of electromagnetic properties is obtained. The systematic behavior of the electromagnetic properties is explained in relation to the drastic change between clustering structure and shell-model-like structure. This explanation gives us an important indication that clustering structure in neutron-rich B nuclei is strongly suggested by the experimental data. It is shown that the structure change with increase of the neutron number is largely governed by the shell effect of neutron orbits. Exotic structure with new type of clustering is suggested to evolve in neutron-rich nuclei near the dripline.

  15. The Subsurface Structure and Density of Cometary Nuclei

    NASA Astrophysics Data System (ADS)

    Lamy, P. L.; Herique, A.; Toth, I.

    2015-12-01

    Little is known about the internal structure and density of cometary nuclei. Indirect evidences available so far are not compelling and these questions essentially remain a matter of speculation. It is therefore important to fully exploit the potential sources of information and this is particularly the case of radar observations which have the capability to probe the first few meters of cometary nuclei when they come sufficiently close to Earth. We review the available results and find that proper data are available for eight nuclei yielding their geometric radar albedo and the dielectric permittivity of their subsurface assuming that the scattering of the radar beam is predominantly specular. The range of permittivity is quite broad, extending from 1.7 to 3.1 although a more realistic interval is probably 2 to 3.1 implying pronounced diversity in the subsurface properties of cometary nuclei. A novel interpretation of these results is performed based on the calculation of the dielectric permittivity of various samples of three-phase mixtures of ice, dust and vacuum using two mixing formulas and on the introduction of ternary diagrams where the three axes correspond to the volumetric fraction of the three phases. The derived values of the permittivity supplemented by a general constraint on the dust-to-ice mass ratio define restricted regions in the ternary diagrams broadly imposing that the ice fraction lies in the range 0.1 to 0.2, the dust fraction in the range 0.2 to 0.5, and the porosity in the range 35 % to 75 %. The density of the subsurface of the considered eight nuclei is only constrained to the broad range 500 to 2000 kg m-3 due to the poorly known density of the dust phase. However, the results unambiguously reveal considerable variation among cometary nuclei of the structure and properties of their subsurface layers.

  16. Isospin-symmetry-breaking effects in A∼70 nuclei within beyond-mean-field approach

    SciTech Connect

    Petrovici, A.; Andrei, O.

    2015-02-24

    Particular isospin-symmetry-breaking probes including Coulomb energy differences (CED), mirror energy differences (MED), and triplet energy differences (TED) manifest anomalies in the A∼70 isovector triplets of nuclei. The structure of proton-rich nuclei in the A∼70 mass region suggests shape coexistence and competition between pairing correlations in different channels. Recent results concerning the interplay between isospin-mixing and shape-coexistence effects on exotic phenomena in A∼70 nuclei obtained within the beyond-mean-field complex Excited Vampir variational model with symmetry projection before variation using a realistic effective interaction in a relatively large model space are presented. Excited Vampir predictions concerning the Gamow-Teller β decay to the odd-odd N=Z {sup 66}As and {sup 70}Br nuclei correlated with the pair structure analysis in the T=1 and T=0 channel of the involved wave functions are discussed.

  17. Localization of chromosome regions in potoroo nuclei ( Potorous tridactylus Marsupialia: Potoroinae).

    PubMed

    Rens, W; O'Brien, P C M; Graves, J A M; Ferguson-Smith, M A

    2003-08-01

    Chromosome paints of the rat kangaroo ( Aepyprymnus rufuscens, 2 n=32) were used to define chromosome regions in the long nosed potoroo ( Potorous tridactylus, 2 n=12 female, 13 male) karyotype and localize these regions in three-dimensionally preserved nuclei of the potoroo to test the hypothesis that marsupial chromosomes have a radial distribution. In human nuclei chromosomes are distributed in a proposed radial fashion. Gene-rich chromosomes in the human interphase nucleus are preferentially located in the central area while gene-poor chromosomes are found more at the periphery of the nucleus; this feature is conserved in primates and chicken. Chromosome ordering in nuclei of P. tridactylus is related to their size and centromere position. Its relationship with replication patterns in interphase nuclei and metaphase was studied. In addition it was observed that the nucleus was not a smooth entity but had projections occupied by specific chromosome regions.

  18. Future of superheavy element research: Which nuclei could be synthesized within the next few years?

    NASA Astrophysics Data System (ADS)

    Zagrebaev, Valeriy; Karpov, Alexander; Greiner, Walter

    2013-03-01

    Low values of the fusion cross sections and very short half-lives of nuclei with Z>120 put obstacles in synthesis of new elements. Different nuclear reactions (fusion of stable and radioactive nuclei, multi-nucleon transfers and neutron capture), which could be used for the production of new isotopes of superheavy (SH) elements, are discussed in the paper. The gap of unknown SH nuclei, located between the isotopes which were produced earlier in the cold and hot fusion reactions, can be filled in fusion reactions of 48Ca with available lighter isotopes of Pu, Am, and Cm. Cross sections for the production of these nuclei are predicted to be rather large, and the corresponding experiments can be easily performed at existing facilities. For the first time, a narrow pathway is found to the middle of the island of stability owing to possible β+-decay of SH isotopes which can be formed in ordinary fusion reactions of stable nuclei. Multi-nucleon transfer processes at near barrier collisions of heavy (and very heavy, U-like) ions are shown to be quite realistic reaction mechanism allowing us to produce new neutron enriched heavy nuclei located in the unexplored upper part of the nuclear map. Neutron capture reactions can be also used for the production of the long-living neutron rich SH nuclei. Strong neutron fluxes might be provided by pulsed nuclear reactors and by nuclear explosions in laboratory conditions and by supernova explosions in nature. All these possibilities are discussed in the paper.

  19. Mass prediction of proton-rich nuclides with the Coulomb displacement energies in the relativistic point-coupling model

    NASA Astrophysics Data System (ADS)

    Sun, BaoHua; Zhao, PengWei; Meng, Jie

    2011-02-01

    The masses, one- and two-proton separation energies of proton-rich nuclei with Z = 20-55, are computed using the measured masses of mirror neutron-rich nuclei and the Coulomb displacement energies calculated from the relativistic point-coupling model. The implications for the proton drip lines, candidates for two-proton emitters, as well as the impact on the astrophysical rp-process are discussed.

  20. Auxiliary Field Diffusion Monte Carlo Calculation of Nuclei with A{<=}40 with Tensor Interactions

    SciTech Connect

    Gandolfi, S.; Pederiva, F.

    2007-07-13

    We calculate the ground-state energy of {sup 4}He, {sup 8}He, {sup 16}O, and {sup 40}Ca using the auxiliary field diffusion Monte Carlo method in the fixed-phase approximation and the Argonne v{sub 6}{sup '} interaction which includes a tensor force. Comparison of our light nuclei results to those of Green's function Monte Carlo calculations shows the accuracy of our method for both open and closed-shell nuclei. We also apply it to {sup 16}O and {sup 40}Ca to show that quantum Monte Carlo methods are now applicable to larger nuclei.

  1. Scissors Mode in Gd Nuclei

    NASA Astrophysics Data System (ADS)

    Kroll, J.; Baramsai, B.; Becker, J. A.; Bečvář, F.; Bredeweg, T. A.; Couture, A.; Chyzh, A.; Dashdorj, D.; Haight, R. C.; Jandel, M.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Parker, W.; Rundberg, R. S.; Ullmann, J. L.; Vieira, G. J.; Walker, C. L.; Wilhelmy, J. B.; Wouters, J. M.; Wu, C. Y.

    2012-02-01

    Spectra of γ rays following neutron capture at isolated resonances of 6 stable Gd isotopes were measured with highly segmented BaF2 detector DANCE at the Los Alamos LANSCE spallation neutron source. The main emphasis was put on studying the γ-cascade decay of neutron resonances to get unique information on photon strength. An analysis of the accumulated γ-ray spectra within the extreme statistical model leads to an inescapable conclusion that scissors mode resonances are built not only on the ground-state, but also on excited levels in all product nuclei studied. The results on summed B(M1)↑ strength and energy of the scissors mode are compared with systematics of scissors mode parameters for the ground-state transitions deduced from nuclear resonance fluorescence measurements. A specific feature of our experiments is the investigation of scissors mode of odd nuclei, for which the nuclear resonance fluorescence provides only limited information.

  2. Dynamics of hot rotating nuclei

    NASA Astrophysics Data System (ADS)

    Garcias, F.; de La Mota, V.; Remaud, B.; Royer, G.; Sébille, F.

    1991-02-01

    The deexcitation of hot rotating nuclei is studied within a microscopic semiclassical transport formalism. This framework allows the study of the competition between the fission and evaporation channels of deexcitation, including the mean-field and two-body interactions, without shape constraint for the fission channel. As a function of initial angular momenta and excitation energies, the transitions between three regimes is analyzed [particle evaporation, binary (ternary) fussion and multifragmentation], which correspond to well-defined symmetry breakings in the inertia tensor of the system. The competition between evaporation and binary fission is studied, showing the progressive disappearance of the fission process with increasing excitation energies, up to a critical point where nuclei pass directly from evaporation to multifragmentation channels.

  3. Direct Reactions with Exotic Nuclei

    SciTech Connect

    Baur, G.; Typel, S.

    2005-10-14

    We discuss recent work on Coulomb dissociation and an effective-range theory of low-lying electromagnetic strength of halo nuclei. We propose to study Coulomb dissociation of a halo nucleus bound by a zero-range potential as a homework problem. We study the transition from stripping to bound and unbound states and point out in this context that the Trojan-Horse method is a suitable tool to investigate subthreshold resonances.

  4. Mass model for unstable nuclei

    SciTech Connect

    Moeller, P.; Nix, J.R.

    1994-02-01

    We present some essential features of a macroscopic-microscopic nuclear-structure model, with special emphasis on the results of a recent global calculation of nuclear masses. We discuss what should be some minimal requirements of a nuclear mass model and study how the macroscopic-microscopic method and other nuclear mass models fulfil such basic requirements. We study in particular the reliability of nuclear mass models in regions of nuclei that were not considered in the determination of the model parameters.

  5. Hydrogen rich gas generator

    NASA Technical Reports Server (NTRS)

    Houseman, J. (Inventor)

    1976-01-01

    A process and apparatus is described for producing a hydrogen rich gas by introducing a liquid hydrocarbon fuel in the form of a spray into a partial oxidation region and mixing with a mixture of steam and air that is preheated by indirect heat exchange with the formed hydrogen rich gas, igniting the hydrocarbon fuel spray mixed with the preheated mixture of steam and air within the partial oxidation region to form a hydrogen rich gas.

  6. Rich catalytic injection

    DOEpatents

    Veninger, Albert

    2008-12-30

    A gas turbine engine includes a compressor, a rich catalytic injector, a combustor, and a turbine. The rich catalytic injector includes a rich catalytic device, a mixing zone, and an injection assembly. The injection assembly provides an interface between the mixing zone and the combustor. The injection assembly can inject diffusion fuel into the combustor, provides flame aerodynamic stabilization in the combustor, and may include an ignition device.

  7. Close supermassive binary black holes.

    PubMed

    Gaskell, C Martin

    2010-01-01

    It has been proposed that when the peaks of the broad emission lines in active galactic nuclei (AGNs) are significantly blueshifted or redshifted from the systemic velocity of the host galaxy, this could be a consequence of orbital motion of a supermassive black-hole binary (SMBB). The AGN J1536+0441 ( = SDSS J153636.22+044127.0) has recently been proposed as an example of this phenomenon. It is proposed here instead that J1536+0441 is an example of line emission from a disk. If this is correct, the lack of clear optical spectral evidence for close SMBBs is significant, and argues either that the merging of close SMBBs is much faster than has generally been hitherto thought, or if the approach is slow, that when the separation of the binary is comparable to the size of the torus and broad-line region, the feeding of the black holes is disrupted. PMID:20054358

  8. Close supermassive binary black holes

    NASA Astrophysics Data System (ADS)

    Gaskell, C. Martin

    2010-01-01

    It has been proposed that when the peaks of the broad emission lines in active galactic nuclei (AGNs) are significantly blueshifted or redshifted from the systemic velocity of the host galaxy, this could be a consequence of orbital motion of a supermassive blackhole binary (SMB). The AGN J1536+0441 (=SDSS J153636.22+044127.0) has recently been proposed as an example of this phenomenon. It is proposed here instead that 1536+044 is an example of line emission from a disc. If this is correct, the lack of clear optical spectral evidence for close SMBs is significant and argues either that the merging of close SMBs is much faster than has generally been hitherto thought, or if the approach is slow, that when the separation of the binary is comparable to the size of the torus and broad-line region, the feeding of the black holes is disrupted.

  9. Fission Properties for R-Process Nuclei

    SciTech Connect

    Erler, J.

    2012-01-01

    We present a systematics of fission barriers and fission lifetimes for the whole landscape of superheavy elements (SHE), i.e., nuclei with Z 100. The fission lifetimes are also compared with the -decay half-lives. The survey is based on a self-consistent description in terms of the Skyrme-Hartree-Fock (SHF) approach. Results for various different SHF parametrizations are compared to explore the robustness of the predictions. The fission path is computed by quadrupole constrained SHF. The computation of fission lifetimes takes care of the crucial ingredients of the large-amplitude collective dynamics along the fission path, as self-consistent collective mass and proper quantum corrections. We discuss the different topologies of fission landscapes which occur in the realm of SHE (symmetric versus asymmetric fission, regions of triaxial fission, bimodal fission, and the impact of asymmetric ground states). The explored region is extended deep into the regime of very neutron-rich isotopes as they are expected to be produced in the astrophysical r process.

  10. Dielectronic Recombination In Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Lukic, D. V.; Schnell, M.; Savin, D. W.; Altun, Z.; Badnell, N.; Brandau, C.; Schmidt, E. W.; Mueller, A.; Schippers, S.; Sprenger, F.; Lestinsky, M.; Wolf, A.

    2006-01-01

    XMM-Newton and Chandra observations of active galactic nuclei (AGN) show rich spectra of X-ray absorption lines. These observations have detected a broad unresolved transition array (UTA) between approx. 15-17 A. This is attributed to inner-shell photoexcitation of M-shell iron ions. Modeling these UTA features is currently limited by uncertainties in the low-temperature dielectronic recombination (DR) data for M-shell iron. In order to resolve this issue, and to provide reliable iron M-shell DR data for plasma modeling, we are carrying out a series of laboratory measurements using the heavy-ion Test Storage Ring (TSR) at the Max-Plank-Institute for Nuclear Physics in Heidelberg, Germany. Currently, laboratory measurements of low temperature DR can only be performed at storage rings. We use the DR data obtained at TSR, to calculate rate coefficients for plasma modeling and to benchmark theoretical DR calculations. Here we report our recent experimental results for DR of Fe XIV forming Fe XIII.

  11. Research: Rags to Rags? Riches to Riches?

    ERIC Educational Resources Information Center

    Bracey, Gerald W.

    2004-01-01

    Everyone has read about what might be called the "gold gap"--how the rich in this country are getting richer and controlling an ever-larger share of the nation's wealth. The Century Foundation has started publishing "Reality Check", a series of guides to campaign issues that sometimes finds gaps in these types of cherished delusions. The guides…

  12. LETTER TO THE EDITOR: The halo structure of neutron-drip line nuclei: (neutron) cluster-core model

    NASA Astrophysics Data System (ADS)

    Gupta, Raj K.; Balasubramaniam, M.; Puri, Rajeev K.; Scheid, Werner

    2000-02-01

    Nuclei at the neutron-drip line are studied. In particular, we analyse the binding energies with the effects of Coulomb repulsion, nuclear attraction due to proximity and rotational energy due to angular momentum. This includes the study of the `neutron-halo structure' of some 18 light neutron-rich nuclei. In terms of the neutron-cluster + core picture, the halo structures of these nuclei are identified which agree with the hypothesis of one/two neutron separation energies and are supported by available experimental information. All the studied nuclei possess 1n- or 2n-halo structure. It is further shown that these nuclei prefer stable cores with not only the neutron number N = 2Z but also with 2Z +/-2.

  13. Beta-decay studies of nuclei far from stability near N=28

    SciTech Connect

    Sorlin, O.; Anne, R.; Axelsson, L.; Bazin, D.; Boehmer, W.; Borrel, V.; Guillemaud-Mueller, D.; Jading, Y.; Keller, H.; Kratz, K.; Lewitowicz, M.; Lukyanov, S.M.; Mehren, T.; Mueller, A.C.; Penionzhkevich, Y.E.; Pfeiffer, B.; Pougheon, F.; Saint-Laurent, M.G.; Salamatin, V.S.; Schoedder, S.; Woehr, A.

    1995-02-05

    Beta-decay half-lives and {beta}-delayed neutron-emission probabilities of the very neutron-rich nuclei {sup 43}P, {sup 42,44,45}S and {sup 44-46}Cl, {sup 47}Ar have been recently measured. These isotopes, which lie at or close to the N=28 magic shell were produced at GANIL in interactions of a 60 MeV/u {sup 48}Ca beam with a {sup 64}Ni target, and were separated by the doubly achromatic spectrometer LISE3. Their decay was studied by a {beta} or {beta}-n time correlation measurement. The results are compared to recent model predictions and indicate a rapid weakening of the N=28 shell below {sup 48}{sub 20}Ca{sub 28}. The nuclear structure effects reflected in the decay properties of the exotic S and Cl isotopes may be the clue for the astrophysical understanding of the unusual {sup 48}Ca/{sup 46}Ca abundance ratio measured in the solar system, or observed in EK-inclusions of the Allende meteorite. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  14. Structure of Exotic Mg Isotopes and Temperature Dependence of the Symmetry Energy of Finite Nuclei

    NASA Astrophysics Data System (ADS)

    Gaidarov, M. K.; Sarriguren, P.; Antonov, A. N.; Kadrev, D. N.; Moya de Guerra, E.

    2016-06-01

    We study various ground-state properties of neutron-rich and neutron-deficient Mg isotopes with A=20-36 in the framework of the self-consistent deformed Skyrme-Hartree- Fock plus BCS method. The nuclear symmetry energy is investigated for the same isotopic chain following the theoretical approach based on the coherent density fluctuation model. The results of the calculations show that the behavior of the nuclear charge radii and the nuclear matter properties in the Mg isotopic chain is closely related to the nuclear deformation. The temperature dependence of the symmetry energy for isotopic chains of even-even Ni (A=58- 82), Sn (A=124-152), and Pb (A=202-214) nuclei is investigated in the framework of the local density approximation. The results for the thermal evolution of the symmetry energy coefficient show that for all isotopic chains considered and for both Skyrme forces used in the calculations the symmetry energy coefficient decreases with the increase of the mass number in the temperature interval T = 0-5 MeV.

  15. Global patterns of species richness and climate

    SciTech Connect

    Currie, D.J. )

    1994-06-01

    Why are there many species in some places and few in others Several studies have shown that the variation in the number of species over continent-sized areas is closely related to the variation in macroclimatic factors: heat and moisture for terrestrial plants, and heat for terrestrial vertebrates. Yet, most of these studies dealt primarily with temperature areas on single continents. If contemporary climate is the principle determinant of large-scale patterns of richness, then richness should be related to climate in similar ways on different continents, regardless of their evolutionary histories. To test the hypothesis, we have gathered published data on the distributions of birds and mammals in temperature and tropical areas. We found that richness varies as a function of potential evapotranspiration in very similar ways on different continents in temperate areas, although there is some significant variation among continents that is unrelated to climate. In tropical areas, richness is more closely related to precipitation and annual climatic variability. Re-analysis of published data on plant richness is consistent with these observations. We conclude that most of the variation in large-scale patterns of species richness can be accounted for by contemporary climate.

  16. The production of proton-rich isotopes beyond iron: The γ-process in stars

    NASA Astrophysics Data System (ADS)

    Pignatari, Marco; Göbel, Kathrin; Reifarth, René; Travaglio, Claudia

    2016-04-01

    Beyond iron, a small fraction of the total abundances in the Solar System is made of proton-rich isotopes, the p-nuclei. The clear understanding of their production is a fundamental challenge for nuclear astrophysics. The p-nuclei constrain the nucleosynthesis in core-collapse and thermonuclear supernovae. The γ-process is the most established scenario for the production of the p-nuclei, which are produced via different photodisintegration paths starting on heavier nuclei. A large effort from nuclear physics is needed to access the relevant nuclear reaction rates far from the valley of stability. This review describes the production of the heavy proton-rich isotopes by the γ-process in stars, and explores the state of the art of experimental nuclear physics to provide nuclear data for stellar nucleosynthesis.

  17. Informing Neutron-Capture Rates through (d,p) Reactions on Neutron-Rich Tin Isotopes

    NASA Astrophysics Data System (ADS)

    Manning, B.; Cizewski, J. A.; Kozub, R. L.; Ahn, S.; Allmond, J. M.; Bardayan, D. W.; Chae, K. Y.; Chipps, K. A.; Howard, M. E.; Jones, K. L.; Liang, J. F.; Matos, M.; Nunes, F. M.; Nesaraja, C. D.; O'Malley, P. D.; Pain, S. D.; Peters, W. A.; Pittman, S. T.; Ratkiewicz, A.; Schmitt, K. T.; Shapira, D.; Smith, M. S.; Titus, L.

    2014-03-01

    Level energies and spectroscopic information for neutron-rich nuclei provide important input for r-process nucleosynthesis calculations; specifically, the location and strength of single-neutron l = 1 states when calculating neutron-capture rates. Surman and collaborators have performed sensitivity studies to show that varying neutron-capture rates can significantly alter final r-process abundances. However, there are many nuclei important to the r-process that cannot be studied. Extending studies to more neutron-rich nuclei will help constrain the nuclear shell-model in extrapolating to nuclei even further from stability. The (d,p) reaction has been measured with radioactive ion beams of 126Sn and 128Sn to complete the set of (d,p) studies on even mass tin isotopes from doubly-magic 132 to stable 124Sn. Work supported in part by the U.S. Department of Energy and National Science Foundation.

  18. Experimental and phenomenological approaches to the structure of exotic nuclei

    SciTech Connect

    Casten, R.F.; Zamfir, N.V. ||

    1995-07-01

    The structure of exotic nuclei that will become accessible with radioactive beams, especially in extremely neutron-rich nuclei where there is a large ``lever arm`` from the valley of stability, is likely to be quite different from anything we have yet encountered. There have been suggestions of radically-different shell structure due, for example, to more-rounded shell potentials (no ``l{sup 2}`` term in the Nilsson potential) or to weaker l{center_dot}s interactions. Also, the weak binding of the outermost nucleons, the coupling to the continuum, changes in residual p-n and pairing interactions, will all contribute to new types of structure and collectivity. Among other effects, magic numbers are likely to lose their robustness; sequences of shell model orbits might be altered in major ways; the onset, manifestations, and evolution of collectivity could be different; unique parity orbits may revert to their parent shells. Radioactive beams will provide the opportunity to study these exotic nuclei, but, at the same time, the amount of data obtainable win be much less than we are accustomed to. Hence, it will be necessary to develop highly-efficient experimental approaches on the one hand, and new signatures of structure, based on the simplest-to-obtain data, on the other. Recently, progress has been made in both areas, and this work is discussed below.

  19. Momentum distributions in light halo nuclei and structure constraints

    NASA Astrophysics Data System (ADS)

    Souza, L. A.; Bellotti, F. F.; Frederico, T.; Yamashita, M. T.; Tomio, Lauro

    2016-03-01

    The core recoil momentum distribution of neutron-rich isotopes of light exotic nuclei is studied within a three-body model, where the nuclei are described by a core and two neutrons, with interactions dominated by the s-wave channel. In our framework, the two-body subsystems should have large scattering lengths in comparison with the interaction range allowing to use a three-body model with a zero-range force. The ground-state halo wave functions in momentum space are obtained by using as inputs the two-neutron separation energy and the energies of the singlet neutron-neutron and neutron-core virtual states. Within our model, we obtain the momentum probability densities for the Borromean exotic nuclei 11Li and 22C. In the case of the core recoil momentum distribution of 11Li, a fair reproduction of the experimental data was obtained, without free parameters, considering only the two-body low-energies. By analysing the obtained core momentum distribution in face of recent experimental data, we verify that such data are constraining the 22C two-neutron separation energy to a value between 100 and 400 keV.

  20. The Array for Nuclear Astrophysics Studies with Exotic Nuclei (anasen)

    NASA Astrophysics Data System (ADS)

    Matos, M.; Blackmon, J. C.; Gardiner, H. E.; Linhardt, L. E.; Macon, K. T.; Mondello, L. L.; Baby, L.; Johnson, E.; Koshchiy, E.; Rogachev, G.; Wiedenhöver, I.; Bardayan, D. W.

    2013-03-01

    Experimental information about most reactions involving short-lived nuclei is limited. New facilities aim to provide wider access to unstable isotopes, but the limited intensities require more efficient and selective techniques and devices. The Array for Nuclear Astrophysics Studies with Exotic Nuclei (ANASEN) is a charged-particle detector array designed primarily for studies of reactions important in the αp- and rp- processes with proton-rich exotic nuclei. The array consists of 40 silicon-strip detectors backed with CsI scintillators. The detectors cover an area of about 1300 cm2 providing essentially complete solid angle coverage for the reactions of interest with good energy and position resolution. ANASEN also includes a position-sensitive annular gas proportional counter that allows it to be used as an active gas target/detector. ANASEN is designed for direct measurement of (α,p) re-actions in inverse kinematics as well as for studies of proton elastic and inelastic scattering, (p, γ) reactions and transfer reactions. The array is being developed by Louisiana State University and Florida State University. Presently it is located at the RESOLUT radioacitve ion beam facility at FSU, where the first experiments are being performed. In the future, the array will be used at the ReA3 facility at the National Superconducting Cyclotron Laboratory.

  1. Mechanisms of quinacrine binding and fluorescence in nuclei and chromosomes.

    PubMed

    Sumner, A T

    1986-01-01

    The mechanisms has been investigated whereby quinacrine binds to the DNA of nuclei and chromosomes in cytological preparations fixed in methanol-acetic acid. A variety of evidence is consistent with the idea that the quinacrine binds by intercalation. This is supported by a high value for the affinity of quinacrine for DNA, together with a saturation value of 0.2 quinacrine molecules/nucleotide; binding in the presence of strong salt solutions; and inhibition of fluorescence and banding by denaturation or depurination of DNA. At high quinacrine concentrations, weak binding of quinacrine to nuclei and chromosomes also occurs, but this is not relevant to the production of strong fluorescence or Q-banding patterns. A number of factors were tested which might have affected quinacrine fluorescence and banding. These included: pH; blocking protein amino groups by acetylation or benzoylation; introduction of hydrophobic groups by benzoylation; and dephosphorylation. All these treatments were without effect. However, comparison of the quinacrine fluorescence of human and onion nuclei, which differ substantially in the base composition of their DNA, shows that quinacrine fluorescence can be enhanced in cytological preparations by AT-rich DNA. PMID:3721920

  2. Deuteron distribution in nuclei and the Levinger's factor

    NASA Astrophysics Data System (ADS)

    Benhar, O.; Fabrocini, A.; Fantoni, S.; Illarionov, A. Yu.; Lykasov, G. I.

    2003-01-01

    We compute the distribution of quasideuterons in doubly closed shell nuclei. The ground states of 16O and 40Ca are described in ls coupling using a realistic Hamiltonian including the Argonne v'8 and the Urbana IX models of two- and three-nucleon potentials, respectively. The nuclear wave function contains central and tensor correlations, and correlated basis functions theory is used to evaluate the distribution of neutron-proton pairs, having the deuteron quantum numbers, as a function of their total momentum. By computing the number of deuteronlike pairs we are able to extract Levinger’s factor and compare to both the available experimental data and the predictions of the local density approximation, based on nuclear matter estimates. The agreement with the experiments is excellent, whereas the local density approximation is shown to sizably overestimate Levinger’s factor in the region of the medium nuclei.

  3. Magnetic moments of light nuclei from lattice quantum chromodynamics

    DOE PAGES

    Beane, S.  R.; Chang, E.; Cohen, S.; Detmold, W.; Lin, H.  W.; Orginos, K.; Parreño, A.; Savage, M.  J.; Tiburzi, B.  C.

    2014-12-16

    We present the results of lattice QCD calculations of the magnetic moments of the lightest nuclei, the deuteron, the triton and 3He, along with those of the neutron and proton. These calculations, performed at quark masses corresponding to mπ ~ 800 MeV, reveal that the structure of these nuclei at unphysically heavy quark masses closely resembles that at the physical quark masses. We find that the magnetic moment of 3He differs only slightly from that of a free neutron, as is the case in nature, indicating that the shell-model configuration of two spin-paired protons and a valence neutron captures itsmore » dominant structure. Similarly a shell-model-like moment is found for the triton, μ3H ~ μp. The deuteron magnetic moment is found to be equal to the nucleon isoscalar moment within the uncertainties of the calculations.« less

  4. Ground states of larger nuclei

    SciTech Connect

    Pieper, S.C.; Wiringa, R.B.; Pandharipande, V.R.

    1995-08-01

    The methods used for the few-body nuclei require operations on the complete spin-isospin vector; the size of this vector makes such methods impractical for nuclei with A > 8. During the last few years we developed cluster expansion methods that do not require operations on the complete vector. We use the same Hamiltonians as for the few-body nuclei and variational wave functions of form similar to the few-body wave functions. The cluster expansions are made for the noncentral parts of the wave functions and for the operators whose expectation values are being evaluated. The central pair correlations in the wave functions are treated exactly and this requires the evaluation of 3A-dimensional integrals which are done with Monte Carlo techniques. Most of our effort was on {sup 16}O, other p-shell nuclei, and {sup 40}Ca. In 1993 the Mathematics and Computer Science Division acquired a 128-processor IBM SP which has a theoretical peak speed of 16 Gigaflops (GFLOPS). We converted our program to run on this machine. Because of the large memory on each node of the SP, it was easy to convert the program to parallel form with very low communication overhead. Considerably more effort was needed to restructure the program from one oriented towards long vectors for the Cray computers at NERSC to one that makes efficient use of the cache of the RS6000 architecture. The SP made possible complete five-body cluster calculations of {sup 16}O for the first time; previously we could only do four-body cluster calculations. These calculations show that the expectation value of the two-body potential is converging less rapidly than we had thought, while that of the three-body potential is more rapidly convergent; the net result is no significant change to our predicted binding energy for {sup 16}O using the new Argonne v{sub 18} potential and the Urbana IX three-nucleon potential. This result is in good agreement with experiment.

  5. β -Decay Half-Lives of 110 Neutron-Rich Nuclei across the N=82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process

    SciTech Connect

    Lorusso, G.; Nishimura, S.; Xu, Z. Y.; Jungclaus, A.; Shimizu, Y.; Simpson, G. S.; Söderström, P. -A.; Watanabe, H.; Browne, F.; Doornenbal, P.; Gey, G.; Jung, H. S.; Meyer, B.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Baba, H.; Benzoni, G.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Inabe, N.; Isobe, T.; Kajino, T.; Kameda, D.; Kim, G. D.; Kim, Y. -K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lane, G. J.; Li, Z.; Montaner-Pizá, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Sakurai, H.; Schaffner, H.; Schury, P.; Shibagaki, S.; Steiger, K.; Suzuki, H.; Takeda, H.; Wendt, A.; Yagi, A.; Yoshinaga, K.

    2015-05-01

    The β -decay half-lives of 110 neutron-rich isotopes of the elements from Rb 37 to Sn 50 were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r -process calculations and reinforce the notion that the second (A≈130 ) and the rare-earth-element (A≈160 ) abundance peaks may result from the freeze-out of an (n,γ)⇌(γ,n) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r -process events.

  6. Relativistic mean-field study on proton skins and proton halos in exotic nuclei

    NASA Astrophysics Data System (ADS)

    Ren, Zhongzhou; Mittig, W.; Sarazin, F.

    1999-06-01

    We investigate the ground state properties of proton-rich nuclei in the framework of the relativistic mean-field model. Calculations show that the experimental proton halo in the nuclei 26,27,28P can be reproduced by the model. The proton halos can appear in proton-rich nuclei because the total nuclear potential is attractive up to the radial distance r ≈ 5.5 fm. But the size of proton halos is finite due to the limitation of the Coulomb potential barrier. The mean-square radius of a halo proton is not very sensitive to the separation energy of the last proton in some very proton-rich nuclei due to the effect of the Coulomb barrier. This behavior is different from the case of a neutron halo where the mean-square radius of a halo neutron is inversely proportional to the separation energy of the last halo neutron. We have also analysed the differences of the relativistic mean-field potentials of 25Al and 26P and found that the isovector potential from the p meson has an important effect on the differences.

  7. The evolution of close binary stars

    NASA Astrophysics Data System (ADS)

    Tutukov, A. V.; Cherepashchuk, A. M.

    2016-05-01

    A review of our current understanding of the physics and evolution of close binary stars with various masses under the influence of the nuclear evolution of their components and their magnetic stellar winds is presented. The role of gravitational-wave radiation by close binaries on their evolution and the loss of their orbital angular momentum is also considered. The final stages in the evolution of close binary systems are described. The review also notes the main remaining tasks related to studies of the physics and evolution of various classes of close binaries, including analyses of collisions of close binaries and supermassive black holes in galactic nuclei. Such a collision could lead to the capture of one of the components by the black hole and the acceleration of the remaining component to relativistic speeds.

  8. Mass Measurements of Proton-rich Nuclides at the Cooler Storage Ring at IMP

    SciTech Connect

    Zhang, Y. H.; Xu, H. S.; Wang, M.; Zhou, X. H.; Yuan, Y. J.; Xia, J. W.; Hu, Z. G.; Huang, W. X.; Liu, Y.; Ma, X.; Mao, R. S.; Mei, B.; Sun, Z. Y.; Wang, J. S.; Xiao, G. Q.; Yan, X. L.; Yang, J. C.; Zhao, H. W.; Zhao, T. C.; Zhang, X. Y.; and others

    2011-11-30

    Recent results and progress of mass measurements of proton-rich nuclei using isochronous mass spectrometry (IMS) are reported. The nuclei under investigation were produced via fragmentation of relativistic energy heavy ions of {sup 78}Kr and {sup 58}Ni. After in-flight separation by the fragment separator RIBLL-2, the nuclei were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of the revolution times. The impact of these measurements on the stellar nucleosynthesis in the rp-process is discussed.

  9. A Comprehensive Approach to Determination of Nuclear Data of Unstable Nuclei

    NASA Astrophysics Data System (ADS)

    Chiba, Satoshi; Nishio, Katsuhisa; Aritomo, Yohihiro; Koura, Hiroyuki; Iwamoto, Osamu; Makii, Hiroyuki; Nishinaka, Ichiro; Hirose, Kentaro

    2016-02-01

    A comprehensive approach to determine nuclear data of unstable nuclei will be described. It consists of a measurement of fission and capture cross sections, mass distribution of fission fragments (independent fission yields) and number of prompt fission neutrons by the method of surrogate reactions. A multi-dimensional Langevin model is being developed to estimate the independent fission yields theoretically. Furthermore, the β decay properties of the fission fragments, almost all are neutron-rich unstable nuclei, are investigated systematically by improving the gross theory of β decay, which will yield information on the decay heat and delayed-neutron data

  10. Nuclear Structure Investigations Of Heavy Nuclei And The Decay Of SHE

    SciTech Connect

    Kuusiniemi, P.

    2005-04-05

    Within the framework of our studies of proton rich nuclei around the N 126 and N = 152 neutron shells we have performed a series of {alpha}-{gamma}-coincidence studies. The nuclei of interest were separated in-flight by the velocity filter SHIP and implanted into a position sensitive 16-strip PIPS-detector where their arrival and subsequent {alpha}-decays were registered. Associated {gamma}-rays were detected by a Ge-Clover-detector. In the present work recent results concerning 216Th and {alpha}-decay chains of 251No and 257Db are given together with brief discussion.

  11. Shape Coexistence in Transitional Nuclei

    NASA Astrophysics Data System (ADS)

    Kulp, W. D.; Schmelzenbach, P.; Wood, J. L.; Allmond, J. M.; Krane, K. S.; Loats, J.; Stapels, C. J.; Norman, E. B.

    2007-10-01

    The ``transitional'' nuclei near N=90 have long been a focus of experimental and theoretical investigations. We report on a program of study of the N=90 and N=88 nuclei with a focus on the structure of ^150Sm elucidated through new high-statistics, precision γ-ray coincidence spectroscopy and γ-γ angular correlation data from the radioactive decay of ^150Pm (T1/2= 2.68 h, Q^- = 3454 keV, J^π= 1^-) and ^150m,gEu (T1/2= 12.8 h, J^π= 0^- and T1/2= 36.9 y, J^π= 5^(-), respectively, Q^+(g.s.)= 2261 keV). In particular, very weak key collective transitions (e.g., the 2^+2(1046) ->4^+1(773) 272 keV γ ray) are observed and precision δ(E2/M1) mixing ratios are extracted (determining δJ = 0 transitions). This data, when combined with published results from conversion electron measurements, two-neutron transfer studies, and Coulomb excitation supports the results from detailed multiple-spectroscopy studies of ^152Sm [1] indicating that shape coexistence underlies the structure at N=88, 90. [1] W. D. Kulp, et al., arXiv:0706.4129 [nucl-ex].

  12. Thermal instability of cell nuclei

    NASA Astrophysics Data System (ADS)

    Warmt, Enrico; Kießling, Tobias R.; Stange, Roland; Fritsch, Anatol W.; Zink, Mareike; Käs, Josef A.

    2014-07-01

    DNA is known to be a mechanically and thermally stable structure. In its double stranded form it is densely packed within the cell nucleus and is thermo-resistant up to 70\\:^\\circ {\\rm{C}}. In contrast, we found a sudden loss of cell nuclei integrity at relatively moderate temperatures ranging from 45 to 55\\:^\\circ {\\rm{C}}. In our study, suspended cells held in an optical double beam trap were heated under controlled conditions while monitoring the nuclear shape. At specific critical temperatures, an irreversible sudden shape transition of the nuclei was observed. These temperature induced transitions differ in abundance and intensity for various normal and cancerous epithelial breast cells, which clearly characterizes different cell types. Our results show that temperatures slightly higher than physiological conditions are able to induce instabilities of nuclear structures, eventually leading to cell death. This is a surprising finding since recent thermorheological cell studies have shown that cells have a lower viscosity and are thus more deformable upon temperature increase. Since the nucleus is tightly coupled to the outer cell shape via the cytoskeleton, the force propagation of nuclear reshaping to the cell membrane was investigated in combination with the application of cytoskeletal drugs.

  13. Physical Processing of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.; Stern, S. Alan

    1997-01-01

    Cometary nuclei preserve a cosmo-chemical record of conditions and processes in the primordial solar nebula, and possibly even the interstellar medium. However, that record is not perfectly preserved over the age of the solar system due to a variety of physical processes which act to modify cometary surfaces and interiors. Possible structural and/or internal processes include: collisional accretion, disruption, and reassembly during formation; internal heating by long and short-lived radionuclides; amorphous to crystalline phase transitions, and thermal stresses. Identified surface modification processes include: irradiation by galactic cosmic rays, solar protons, UV photons, and the Sun's T Tauri stage mass outflow; heating by passing stars and nearby supernovae; gardening by debris impacts; the accretion of interstellar dust and gas and accompanying erosion by hypervelocity dust impacts and sputtering; and solar heating with accompanying crust formation. These modification processes must be taken into account in both the planning and the interpretation of the results of a Comet Nucleus Sample Return Mission. Sampling of nuclei should be done at as great a depth below the surface crust as technically feasible, and at vents or fissures leading to exposed volatiles at depth. Samples of the expected cometary crust and near-surface layers also need to be returned for analysis to achieve a better understanding of the effects of these physical processes. We stress that comets are still likely less modified dm any other solar system bodies, but the degree of modification can vary greatly from one comet to the next.

  14. The fate of ultrahigh energy nuclei in the immediate environment of young fast-rotating pulsars

    SciTech Connect

    Kotera, Kumiko; Amato, Elena; Blasi, Pasquale E-mail: amato@arcetri.astro.it

    2015-08-01

    Young, fast-rotating neutron stars are promising candidate sources for the production of ultrahigh energy cosmic rays (UHECRs). The interest in this model has recently been boosted by the latest chemical composition measurements of cosmic rays, that seem to show the presence of a heavy nuclear component at the highest energies. Neutrons stars, with their metal-rich surfaces, are potentially interesting sources of such nuclei, but some open issues remain: 1) is it possible to extract these nuclei from the star's surface? 2) Do the nuclei survive the severe conditions present in the magnetosphere of the neutron star? 3) What happens to the surviving nuclei once they enter the wind that is launched outside the light cylinder? In this paper we address these issues in a quantitative way, proving that for the most reasonable range of neutron star surface temperatures (T<10{sup 7} K), a large fraction of heavy nuclei survive photo-disintegration losses. These processes, together with curvature losses and acceleration in the star's electric potential, lead to injection of nuclei with a chemical composition that is mixed, even if only iron is extracted from the surface. We show that under certain conditions the chemical composition injected into the wind region is compatible with that required in previous work based on purely phenomenological arguments (typically ∼50% protons, ∼30% CNO and ∼20% Fe), and provides a reasonable explanation of the mass abundance inferred from ultra high energy data.

  15. Review of metastable states in heavy nuclei.

    PubMed

    Dracoulis, G D; Walker, P M; Kondev, F G

    2016-07-01

    The structure of nuclear isomeric states is reviewed in the context of their role in contemporary nuclear physics research. Emphasis is given to high-spin isomers in heavy nuclei, with [Formula: see text]. The possibility to exploit isomers to study some of the most exotic nuclei is a recurring theme. In spherical nuclei, the role of octupole collectivity is discussed in detail, while in deformed nuclei the limitations of the K quantum number are addressed. Isomer targets and isomer beams are considered, along with applications related to energy storage, astrophysics, medicine, and experimental advances. PMID:27243336

  16. Review of metastable states in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Dracoulis, G. D.; Walker, P. M.; Kondev, F. G.

    2016-07-01

    The structure of nuclear isomeric states is reviewed in the context of their role in contemporary nuclear physics research. Emphasis is given to high-spin isomers in heavy nuclei, with A≳ 150 . The possibility to exploit isomers to study some of the most exotic nuclei is a recurring theme. In spherical nuclei, the role of octupole collectivity is discussed in detail, while in deformed nuclei the limitations of the K quantum number are addressed. Isomer targets and isomer beams are considered, along with applications related to energy storage, astrophysics, medicine, and experimental advances.

  17. Interactions of heavy nuclei, Kr, Xe and Ho, in light targets

    NASA Technical Reports Server (NTRS)

    Kertzman, M. P.; Klarmann, J.; Newport, B. J.; Stone, E. C.; Waddington, C. J.; Binns, W. R.; Garrard, T. L.; Israel, M. H.

    1985-01-01

    Over the past few years, the HEAO-3 measurements of the abundance of ultra-heavy cosmic ray nuclei (Z 26) at Earth were analyzed. In order to interpret these abundances in terms of a source composition, allowances must be made for the propagation of the nuclei in the interstellar medium. Vital to any calculation of the propagation is a knowlege of the total and partial interaction cross sections for these heavy nuclei on hydrogen. Until recently, data on such reactions have been scarce. The semi-empirical formalism of Silberberg and Tsao were relied upon to predict the partial cross sections. However, now that relativistic heavy ion beams are available at the LBL Bevalac, some of the cross sections of interest can be measured at energies close to those of the cosmic ray nuclei being observed.

  18. Multispectral comparison of water ice deposits observed on cometary nuclei

    NASA Astrophysics Data System (ADS)

    Oklay Vincent, Nilda; Sunshine, Jessica M.; Pajola, Maurizio; Pommerol, Antoine; Vincent, Jean-Baptiste; Sierks, Holger; OSIRIS Team

    2016-10-01

    Cometary missions Deep Impact, EPOXI and Rosetta investigated the nuclei of comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko respectively. Each of these three missions was equipped with multispectral cameras, allowing imaging at various wavelengths from NUV to NIR. In this spectral range, water ice-rich features display bluer spectral slopes than the average surface and some have very flat spectra. Features enriched in water ice are bright in the monochromatic images and are blue in the RGB color composites generated by using images taken in NUV, visible and NIR wavelentghs. Using these properties, water ice-rich features were detected on the nuclei of comets 9P [1], 103P [2] and 67P [3] via multispectral imaging cameras. Moreover, there were visual detections of jets and outbursts associated to some of these water ice-rich features when the right observing conditions were fulfilled [4, 5].We analyzed multispectral properties of different types of water ice-rich features [3] observed via OSIRIS NAC on comet 67P in the wavelength range of 260 nm to 1000 nm and then compared with those observed on comets 9P and 103P. Our multispectral analysis shows that the water ice deposits observed on comet 9P are very similar to the large bright blue clusters observed on comet 67P, while the large water ice deposit observed on comet 103P is similar to the large isolated water ice-rich features observed on comet 67P. The ice-rich deposits on comet 103P are the bluest of any comet, which indicates that the deposits on 103P contain more water ice than the ones observed on comets 9P and 67P [6].[1] Sunshine et al 2006, Science[2] Sunshine et al 2011, LPSC[3] Pommerol et al 2015, A&A[4] Oklay et al 2016, A&A[5] Vincent et al 2016, A&A[6] Oklay et al 2016, submitted

  19. Short-lived Isotopes from a Close-by AGB Star Triggering the Protosolar Nebula

    NASA Astrophysics Data System (ADS)

    Gallino, R.; Busso, M.; Wasserburg, G. J.; Straniero, O.

    The presence of short-lived isotopes in the early solar system, in particular 26Al, 41Ca, 60Fe, and 107Pd, point to a close-by and fresh nucleosynthesis source, possibly triggering the collapse of the protosolar nebula. We present the results of nucleosynthesis calculations based on an AGB polluting hypothesis. A general concordance of the predicted yields of the above radioactivities relative to 26Al can be obtained in the case of an intermediate mass AGB star with hot bottom burning in the envelope (thus producing 26Al), and mixing through a series of third dredge-up episodes a fraction of the C-rich and s-processed material from the He intershell with the extended envelope. Polution of the protosolar nebula with freshly synthesized material may derive from the efficient winds of the AGB star. In AGB stars, the s-process nucleosynthesis occurs both during the maximum phase of every thermal runaway, driven by the partial activation of the 22Ne(alpha,n)25Mg reaction, and in the interpulse phase, where the 13C nuclei are fully consumed in radiative conditions by the activation of the 13C(alpha,n)16O reaction. We have used different prescriptions for the amount of the 13C nuclei present in the intershell. A minimum amount of 13C is naturally expected in the ashes of H-shell burning. Possible formation of an extra "13C-pocket" derives from the injection of a small amount of protons from the envelope into the 12C-rich intershell during any third dredge-up episode, when the H-shell is inactivated. Prediction for other short-lived, 36Cl, 135Cs, and 205Pb, are given. General consequences for the pollution of the protosolar nebula with newly synthesized stable isotopes from the AGB winds are outlined. The origin of other detected short-lived nuclei, in particular 53Mn, 129I, and 182Hf, which cannot come from an AGB source, is analysed. The alternative trigger hypothesis by a close-by Supernova is discussed.

  20. Trap-assisted studies of odd, neutron-rich isotopes from Tc to Pd

    NASA Astrophysics Data System (ADS)

    Kurpeta, J.; Jokinen, A.; Penttilä, H.; Płochocki, A.; Rissanen, J.; Urban, W.; Äystö, J.

    2014-01-01

    We review the present and future of trap-assisted structure studies of odd, neutron-rich Tc, Ru, Rh and Pd isotopes at the limits of present experimental techniques. These nuclei of refractory elements are produced in light-particle induced fission and filtered by their mass number with the IGISOL mass separator. Further mass separation with the JYFLTRAP Penning trap system provides a clean, monoisotopic beam perfectly suited for precise nuclear spectroscopy. Connecting the IGISOL and the JYFLTRAP facilities to the recently installed MCC30/15 cyclotron opens new prospects for post-trap spectroscopy of very exotic, neutron-rich nuclei.

  1. Temporomandibular Joint, Closed

    MedlinePlus

    ... Oral Health > The Temporomandibular Joint, Closed The Temporomandibular Joint, Closed Main Content Title: The Temporomandibular Joint, Closed Description: The temporomandibular joint connects the lower ...

  2. Reaction theory for exotic nuclei

    SciTech Connect

    Bonaccorso, Angela

    2014-05-09

    Exotic nuclei are usually defined as those with unusual N/Z ratios. They can be found in the crust of neutron stars enbedded in a sea of electrons or created in laboratory by fragmentation of a primary beam (in-flight method) or of the target (ISOL method). They are extremely important for nuclear astrophysics, see for example Ref.[1]. Furthermore by studying them we can check the limits of validity of nuclear reaction and structure models. This contribution will be devoted to the understanding of how by using reaction theory and comparing to the data we can extract structure information. We shall discuss the differences between the mechanisms of transfer and breakup reactions, an we will try to explain how nowadays it is possible to do accurate spectroscopy in extreme conditions.

  3. The Physics of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Whipple, Fred L.

    1997-01-01

    The recent developments in cometary studies suggest rather low mean densities and weak structures for the nuclei. They appear to be accumulations of fairly discrete units loosely bound together, as deduced from the observations of Comet Shoemaker-Levy 9 during its encounter with Jupiter. The compressive strengths deduced from comet splitting by Opik and Sekanina are extremely low. These values are confirmed by theory developed here. assuming that Comet P/Holmes had a companion that collided with it in 1892. There follows a short discussion that suggests that the mean densities of comets should increase with comet dimensions. The place of origin of short-period comets may relate to these properties.

  4. Theory of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shields, G. A.

    1986-01-01

    The involvement of accretion disks around supermassive black holes in the theory of active galactic nuclei (AGN) is discussed. The physics of thin and thick accretion disks is discussed and the partition between thermal and nonthermal energy production in supermassive disks is seen as uncertain. The thermal limit cycle may operate in supermassive disks (Shields, 1985), with accumulation of gas in the disk for periods of 10 to the 4th to 10 to the 7th years, punctuated by briefer outbursts during which the mass is rapidly transferred to smaller radii. An extended X-ray source in AGN is consistent with observations (Tennant and Mushotsky, 1983), and a large wind mass loss rate exceeding the central accretion rate means that only a fraction of the mass entering the disk will reach the central object; the rest being lost to the wind. Controversy in the relationship between the broad lines and the disk is also discussed.

  5. Single Pion production from Nuclei

    SciTech Connect

    Singh, S. K.; Athar, M. Sajjad; Ahmed, S.

    2007-12-21

    We have studied charged current one pion production induced by {nu}{sub {mu}}({nu}-bar{sub {mu}}) from some nuclei. The calculations have been done for the incoherent pion production processes from these nuclear targets in the {delta} dominance model and take into account the effect of Pauli blocking, Fermi motion and renormalization of {delta} properties in the nuclear medium. The effect of final state interactions of pions has also been taken into account. The numerical results have been compared with the recent results from the MiniBooNE experiment for the charged current 1{pi} production, and also with some of the older experiments in Freon and Freon-Propane from CERN.

  6. Measurement of picosecond lifetimes in neutron-rich Xe isotopes

    NASA Astrophysics Data System (ADS)

    Ilieva, S.; Kröll, Th.; Régis, J.-M.; Saed-Samii, N.; Blanc, A.; Bruce, A. M.; Fraile, L. M.; de France, G.; Hartig, A.-L.; Henrich, C.; Ignatov, A.; Jentschel, M.; Jolie, J.; Korten, W.; Köster, U.; Lalkovski, S.; Lozeva, R.; Mach, H.; Mǎrginean, N.; Mutti, P.; Paziy, V.; Regan, P. H.; Simpson, G. S.; Soldner, T.; Thürauf, M.; Ur, C. A.; Urban, W.; Warr, N.

    2016-09-01

    Background: Lifetimes of nuclear excited states in fission fragments have been studied in the past following isotope separation, thus giving access mainly to the fragments' daughters and only to long-lived isomeric states in the primary fragments. For the first time now, short-lived excited states in the primary fragments, produced in neutron-induced prompt fission of 235U and 241Pu, were studied within the EXILL&FATIMA campaign at the intense neutron-beam facility of the Institute Laue-Langevin in Grenoble. Purpose: We aim to investigate the quadrupole collective properties of neutron-rich even-even 138,140,142Xe isotopes lying between the double shell closure N =82 and Z =50 and a deformed region with octupole collectivity. Method: The γ rays emitted from the excited fragments were detected with a mixed array consisting of 8 HPGe EXOGAM Clover detectors (EXILL) and 16 LaBr3(Ce) fast scintillators (FATIMA). The detector system has the unique ability to select the interesting fragment making use of the high resolution of the HPGe detectors and determine subnanosecond lifetimes using the fast scintillators. For the analysis the generalized centroid difference method was used. Results: We show that quadrupole collectivity increases smoothly with increasing neutron number above the closed N =82 neutron shell. Our measurements are complemented by state-of-the-art theory calculations based on shell-model descriptions. Conclusions: The observed smooth increase in quadrupole collectivity is similar to the evolution seen in the measured masses of the xenon isotopic chain and is well reproduced by theory. This behavior is in contrast to higher Z even-even nuclei where abrupt change in deformation occurs around N =90 .

  7. The mysterious microcircuitry of the cerebellar nuclei

    PubMed Central

    Uusisaari, Marylka; De Schutter, Erik

    2011-01-01

    Abstract The microcircuitry of cerebellar cortex and, in particular, the physiology of its main element, the Purkinje neuron, has been extensively investigated and described. However, activity in Purkinje neurons, either as single cells or populations, does not directly mediate the cerebellar effects on the motor effector systems. Rather, the result of the entire cerebellar cortical computation is passed to the relatively small cerebellar nuclei that act as the final, integrative processing unit in the cerebellar circuitry. The nuclei ultimately control the temporal and spatial features of the cerebellar output. Given this key role, it is striking that the internal organization and the connectivity with afferent and efferent pathways in the cerebellar nuclei are rather poorly known. In the present review, we discuss some of the many critical shortcomings in the understanding of cerebellar nuclei microcircuitry: the extent of convergence and divergence of the cerebellar cortical pathway to the various cerebellar nuclei neurons and subareas, the possible (lack of) conservation of the finely-divided topographical organization in the cerebellar cortex at the level of the nuclei, as well as the absence of knowledge of the synaptic circuitry within the cerebellar nuclei. All these issues are important for predicting the pattern-extraction and encoding capabilities of the cerebellar nuclei and, until resolved, theories and models of cerebellar motor control and learning may err considerably. PMID:21521761

  8. Hybrid theory and calculation of e-N2 scattering. [quantum mechanics - nuclei (nuclear physics)

    NASA Technical Reports Server (NTRS)

    Chandra, N.; Temkin, A.

    1975-01-01

    A theory of electron-molecule scattering was developed which was a synthesis of close coupling and adiabatic-nuclei theories. The theory is shown to be a close coupling theory with respect to vibrational degrees of freedom but is a adiabatic-nuclei theory with respect to rotation. It can be applied to any number of partial waves required, and the remaining ones can be calculated purely in one or the other approximation. A theoretical criterion based on fixed-nuclei calculations and not on experiment can be given as to which partial waves and energy domains require the various approximations. The theory allows all cross sections (i.e., pure rotational, vibrational, simultaneous vibration-rotation, differential and total) to be calculated. Explicit formulae for all the cross sections are presented.

  9. High spin spectroscopy of near spherical nuclei: Role of intruder orbitals

    SciTech Connect

    Bhattacharyya, S.; Bhattacharjee, T.; Mukherjee, G.; Banerjee, D.; Das, S. K.; Guin, R.; Gupta, S. Das

    2014-08-14

    High spin states of nuclei in the vicinity of neutron shell closure N = 82 and proton shell closure Z = 82 have been studied using the Clovere Ge detectors of Indian National Gamma Array. The shape driving effects of proton and neutron unique parity intruder orbitals for the structure of nuclei around the above shell closures have been investigated using light and heavy ion beams. Lifetime measurements of excited states in {sup 139}Pr have been done using pulsed-beam-γ coincidence technique. The prompt spectroscopy of {sup 207}Rn has been extended beyond the 181μs 13/2{sup +} isomer. Neutron-rich nuclei around {sup 132}Sn have been produced from proton induced fission of {sup 235}U and lifetime measurement of low-lying states of odd-odd {sup 132}I have been performed from offline decay.

  10. A statistical approach to describe highly excited heavy and superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Chen, Peng-Hui; Feng, Zhao-Qing; Li, Jun-Qing; Zhang, Hong-Fei

    2016-09-01

    A statistical approach based on the Weisskopf evaporation theory has been developed to describe the de-excitation process of highly excited heavy and superheavy nuclei, in particular for the proton-rich nuclei. The excited nucleus is cooled by evaporating γ-rays, light particles (neutrons, protons, α etc) in competition with binary fission, in which the structure effects (shell correction, fission barrier, particle separation energy) contribute to the processes. The formation of residual nuclei is evaluated via sequential emission of possible particles above the separation energies. The available data of fusion-evaporation excitation functions in the 28Si+198Pt reaction can be reproduced nicely within the approach. Supported by Major State Basic Research Development Program in China (2015CB856903), National Natural Science Foundation of China Projects (11175218, U1332207, 11475050, 11175074), and Youth Innovation Promotion Association of Chinese Academy of Sciences

  11. Sensitivity of p-Nuclei to (n,g) Reaction Rates

    NASA Astrophysics Data System (ADS)

    Scriven, Dustin; Naqvi, Farheen; Spyrou, Artemis; Simon, Anna; Mayer, Brad

    2015-10-01

    The astrophysical p-process, which is responsible for the creation of the proton-rich p-nuclei, is still not well understood. A sensitivity study of p-nuclei abundances to (n, γ) and (γ,n) reaction rates was conducted at the National Superconducting Cyclotron Laboratory using a nuclear reaction network created at Clemson University. This network simulates the explosive shock front of a Type II supernova passing through the oxygen/neon layer of a 25 M⊙ star. Reaction rates of many (n, γ) reactions and their inverses were increased and decreased by a factor of 3 and the effects were observed. Probing the sensitivity of p-nuclei abundances aids in pointing out reactions important to the p-process. In turn, this information can be used as a tool to drive experimental research, helping to decrease uncertainties and increase the robustness of p-process and other stellar models.

  12. Superheavy nuclei and quasi-atoms produced in collisions of transuranium ions

    SciTech Connect

    Zagrebaev, V.I.; Oganessian, Yu.Ts.; Itkis, M.G.; Greiner, Walter

    2006-03-15

    Low energy collisions of very heavy nuclei ({sup 238}U+{sup 238}U, {sup 232}Th+{sup 250}Cf, and {sup 238}U+{sup 248}Cm) have been studied within the realistic dynamical model based on multidimensional Langevin equations. Large charge and mass transfer was found to result from the 'inverse quasi-fission' process leading to the formation of the surviving superheavy long-lived neutron-rich nuclei. In many events, the lifetime of the composite system consisting of two touching nuclei turns out to be rather long; sufficiently long for the spontaneous formation of positrons to occur from a super-strong electric field - a fundamental QED process.

  13. The CBM RICH detector

    NASA Astrophysics Data System (ADS)

    Adamczewski-Musch, J.; Akishin, P.; Becker, K.-H.; Belogurov, S.; Bendarouach, J.; Boldyreva, N.; Chernogorov, A.; Deveaux, C.; Dobyrn, V.; Dürr, M.; Eschke, J.; Förtsch, J.; Heep, J.; Höohne, C.; Kampert, K.-H.; Kochenda, L.; Kopfer, J.; Kravtsov, P.; Kres, I.; Lebedev, S.; Lebedeva, E.; Leonova, E.; Linev, S.; Mahmoud, T.; Michel, J.; Miftakhov, N.; Niebur, W.; Ovcharenko, E.; Pauly, C.; Pfeifer, D.; Querchfeld, S.; Rautenberg, J.; Reinecke, S.; Riabov, Y.; Roshchin, E.; Samsonov, V.; Tarasenkova, O.; Traxler, M.; Ugur, C.; Vznuzdaev, E.; Vznuzdaev, M.

    2016-05-01

    The CBM RICH detector will use CO2 as radiator gas, focussing glass mirrors with Al+MgF2 reflective and protective coating and Hamamatsu H12700 MAPMTs as photon detectors. The detector will serve for electron to pion separation up to momenta of 8 GeV/c and thus enable in CBM the measurement of electromagnetic radiation from the early and dense fireball in A+A collisions at SIS 100. In this article, the current status of the CBM RICH development will be presented including new measurements of the radiation hardness of the H12700 MAPMT and WLS coatings with p-terphenyl, the new concept for the readout electronics, and optimizations ongoing with respect to the mirror mount structure and overall geometry. Prior to the usage in CBM, part of the already ordered MAPMTs will be used to upgrade the HADES RICH detector for a new measurement campaign at SIS 18 from 2018-2020.

  14. Extrasolar Comets in our Solar System Captured During Close Encounters with Nearby Stars?

    NASA Astrophysics Data System (ADS)

    Rocca, M. C. L.; Acevedo, R. D.

    2014-09-01

    It is a fact that many nearby Sun like stars have their own cometary clouds. Close encounters with passing nearby stars may induce to the capture and exchange of cometary nuclei between the Sun and the coming star.

  15. Hydrogen rich gas generator

    NASA Technical Reports Server (NTRS)

    Houseman, J.; Rupe, J. H.; Kushida, R. O. (Inventor)

    1976-01-01

    A process and apparatus is described for producing a hydrogen rich gas by injecting air and hydrocarbon fuel at one end of a cylindrically shaped chamber to form a mixture and igniting the mixture to provide hot combustion gases by partial oxidation of the hydrocarbon fuel. The combustion gases move away from the ignition region to another region where water is injected to be turned into steam by the hot combustion gases. The steam which is formed mixes with the hot gases to yield a uniform hot gas whereby a steam reforming reaction with the hydrocarbon fuel takes place to produce a hydrogen rich gas.

  16. Production cross sections of neutron rich isotopes from a 82Se beam

    NASA Astrophysics Data System (ADS)

    Tarasov, O. B.; Morrissey, D. J.; Amthor, A. M.; Bandura, L.; Baumann, T.; Bazin, D.; Berryman, J. S.; Chubarian, G.; Fukuda, N.; Gade, A.; Ginter, T. N.; Hausmann, M.; Inabe, N.; Kubo, T.; Pereira, J.; Portillo, M.; Sherrill, B. M.; Stolz, A.; Sumithrarachchi, C.; Thoennessen, M.; Weisshaar, D.

    2013-03-01

    Production cross sections for neutron-rich nuclei from the fragmentation of a 82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions of 122 neutron-rich isotopes of elements 11 <= Z <= 32 were determined by varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei including several isotopes first observed in this work. These are the most neutron-rich nuclides of the elements 22 <= Z <= 25 (64Ti, 67V, 69Cr, 72Mn). One event was registered consistent with 70Cr, and another one with 75Fe. A one-body Qg systematics is used to describe the production cross sections based on thermal evaporation from excited prefragments. The current results confirm those of our previous experiment with a 76Ge beam: enhanced production cross sections for neutron-rich fragments near Z = 20.

  17. Fusion probability in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Banerjee, Tathagata; Nath, S.; Pal, Santanu

    2015-03-01

    Background: Fusion between two massive nuclei is a very complex process and is characterized by three stages: (a) capture inside the potential barrier, (b) formation of an equilibrated compound nucleus (CN), and (c) statistical decay of the CN leading to a cold evaporation residue (ER) or fission. The second stage is the least understood of the three and is the most crucial in predicting yield of superheavy elements (SHE) formed in complete fusion reactions. Purpose: A systematic study of average fusion probability, , is undertaken to obtain a better understanding of its dependence on various reaction parameters. The study may also help to clearly demarcate onset of non-CN fission (NCNF), which causes fusion probability, PCN, to deviate from unity. Method: ER excitation functions for 52 reactions leading to CN in the mass region 170-220, which are available in the literature, have been compared with statistical model (SM) calculations. Capture cross sections have been obtained from a coupled-channels code. In the SM, shell corrections in both the level density and the fission barrier have been included. for these reactions has been extracted by comparing experimental and theoretical ER excitation functions in the energy range ˜5 %-35% above the potential barrier, where known effects of nuclear structure are insignificant. Results: has been shown to vary with entrance channel mass asymmetry, η (or charge product, ZpZt ), as well as with fissility of the CN, χCN. No parameter has been found to be adequate as a single scaling variable to determine . Approximate boundaries have been obtained from where starts deviating from unity. Conclusions: This study quite clearly reveals the limits of applicability of the SM in interpreting experimental observables from fusion reactions involving two massive nuclei. Deviation of from unity marks the beginning of the domain of dynamical models of fusion. Availability of precise ER cross

  18. Star formation around active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Keel, William C.

    1987-01-01

    Active galactic nuclei (Seyfert nuclei and their relatives) and intense star formation can both deliver substantial amounts of energy to the vicinity of a galactic nucleus. Many luminous nuclei have energetics dominated by one of these mechanisms, but detailed observations show that some have a mixture. Seeing both phenomena at once raises several interesting questions: (1) Is this a general property of some kinds of nuclei? How many AGNs have surround starbursts, and vice versa? (2) As in 1, how many undiscovered AGNs or starbursts are hidden by a more luminous instance of the other? (3) Does one cause the other, and by what means, or do both reflect common influences such as potential well shape or level of gas flow? (4) Can surrounding star formation tell us anything about the central active nuclei, such as lifetimes, kinetic energy output, or mechanical disturbance of the ISM? These are important points in the understanding of activity and star formation in galactic nuclei. Unfortunately, the observational ways of addressing them are as yet not well formulated. Some preliminary studies are reported, aimed at clarifying the issues involved in study of the relationships between stellar and nonstellar excitement in galactic nuclei.

  19. Shell Model Based Reaction Rates for rp-PROCESS Nuclei in the Mass Range A=44-63

    NASA Astrophysics Data System (ADS)

    Fisker, J. L.; Barnard, V.; Görres, J.; Langanke, K.; Martínez-Pinedo, G.; Wiescher, M. C.

    2001-11-01

    We have used large-scale shell-model diagonalization calculations to determine the level spectra, proton spectroscopic factors, and electromagnetic transition probabilities for proton rich nuclei in the mass range A=44-63. Based on these results and the available experimental data, we calculated the resonances for proton capture reactions on neutron deficient nuclei in this mass range. We also calculated the direct capture processes on these nuclei in the framework of a Woods-Saxon potential model. Taking into account both resonant and direct contributions, we determined the ground-state proton capture reaction rates for these nuclei under hot hydrogen burning conditions for temperatures between 108 and 1010 K. The calculated compound-nucleus level properties and the reaction rates are presented here; the rates are also available in computer-readable format from the authors.

  20. The Stellar Populations of Nuclei, Globular Clusters, and Stars in dE Galaxies in Virgo and Fornax

    NASA Astrophysics Data System (ADS)

    Whitfield Miller, Bryan; Hyazinth Puzia, Thomas; Hilker, Michael; Sanchez-Janssen, Ruben; Kissler-Patig, Markus

    2015-08-01

    We present ages and metallicities for globular clusters, nuclei, and underlying stars in nucleated dwarf elliptical galaxies (dE,N) in the Virgo and Fornax Cluster based on Lick/IDS index measurements and SSP models. Gemini/GMOS spectroscopy shows that the globular clusters are mostly old and metal-poor, very similar to the globular clusters in the Milky Way halo. The nuclei and underlying stars tend to be more metal-rich than the globular clusters and have a wide range of ages. The [α/Fe] ratios for both the globular clusters and nuclei range between 0.0 and 0.3. Formation scenarios for globular clusters and nuclei will be discussed.

  1. Interactions of heavy nuclei, Kr, Xe and Ho, in light targets

    NASA Technical Reports Server (NTRS)

    Kertzman, M. P.; Klarmann, J.; Newport, B. J.; Stone, E. C.; Waddington, C. J.; Binns, W. R.; Garrard, T. L.; Israel, M. H.

    1985-01-01

    Over the past few years, the HEAO-3 measurements of the abundances of ultra-heavy cosmic ray nuclei (Z 26) at earth have been analyzed. In order to interpret these abundances in terms of a source composition, allowance must be made for the propagation of the nuclei in the interstellar medium. Vital to any calculation of the propagation is a knowlege of the total and partial interaction cross sections for these heavy nuclei on hydrogen. Until recently, data on such reactions have been scarce. However, now that relativistic heavy ion beams are available at the LBL Bevalac, some of the cross sections of interest can be measured at energies close to those of the cosmic ray nuclei being observed. During a recent calibration at the Bevalac of an array similar to the HEAO-C3 UH-nuclei detector, targets of raphite (C), polyethylene (CH2), and aluminum were exposed to five heavy ion beams ranging in charge (Z) from 36 to 92. Total and partial charge changing cross sections for the various beam nuclei on hydrogen can be determined from the measured cross sections on C and CH2, and will be applied to the propagation problem. The cross sections on Al can be used to correct the abundances of UH cosmic rays observed in the HEAO C-3 detector for interactions in the detector itself.

  2. Inferring Nuclear Structure Trends of r-PROCESS Nuclei from β-DECAY Measurements

    NASA Astrophysics Data System (ADS)

    Pereira, J.

    2013-03-01

    The present paper reports on several r-process motivated β-decay experiments undertaken at the National Superconducting Cyclotron Laboratory. β-decay half-lives and β-delayed neutron-emission probabilities were measured for neutron-rich nuclei in the region A=80-110. The data are discussed on the basis of quasi-random phase approximation calculations. The emphasis is made on the impact of these data upon calculations of r-process abundances.

  3. Molecular outflows in starburst nuclei

    NASA Astrophysics Data System (ADS)

    Roy, Arpita; Nath, Biman B.; Sharma, Prateek; Shchekinov, Yuri

    2016-08-01

    Recent observations have detected molecular outflows in a few nearby starburst nuclei. We discuss the physical processes at work in such an environment in order to outline a scenario that can explain the observed parameters of the phenomenon, such as the molecular mass, speed and size of the outflows. We show that outflows triggered by OB associations, with NOB ≥ 105 (corresponding to a star formation rate (SFR)≥1 M⊙ yr-1 in the nuclear region), in a stratified disk with mid-plane density n0 ˜ 200-1000 cm-3 and scale height z0 ≥ 200(n0/102 cm-3)-3/5 pc, can form molecules in a cool dense and expanding shell. The associated molecular mass is ≥107 M⊙ at a distance of a few hundred pc, with a speed of several tens of km s-1. We show that a SFR surface density of 10 ≤ ΣSFR ≤ 50 M⊙ yr-1 kpc-2 favours the production of molecular outflows, consistent with observed values.

  4. Unbound Resonances in Light Nuclei

    NASA Astrophysics Data System (ADS)

    Havens, Elizabeth; Finck, Joseph; Gueye, Paul; Thoennessen, Michael; MoNA Collaboration

    2014-09-01

    Currently there has been no comprehensive study undertaken to compile experimental results from neutron unbound spectroscopy using invariant mass measurements, gamma resolutions, and half-lives. At Central Michigan University, Hampton University, and the NSCL, a project was initiated to catalog all unbound resonances in light nuclei (Z = 1-12). Unbound resonances were characterized by having a confirmed neutron decay branch and/or an energy level greater than the neutron binding energy listed for that isotope according to either the National Nuclear Data Center's Evaluated Nuclear Structure Files or Experimental Unevaluated Nuclear Data List and the referred journals therein. Unbound resonances will be presented for twelve elements: H, He, Li, Be, B, C, N, O, Fl, Ne, Na, and Mg. The isotopes in which unbound resonances occur will be identified, along with unbound energy levels for these isotopes. If known, each unbound resonance's gamma resolution, half-life, method of production and journal reference were also determined and a selection of these will be presented.

  5. Neurotransmitters of the suprachiasmatic nuclei

    PubMed Central

    Reghunandanan, Vallath; Reghunandanan, Rajalaxmy

    2006-01-01

    There has been extensive research in the recent past looking into the molecular basis and mechanisms of the biological clock, situated in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. Neurotransmitters are a very important component of SCN function. Thorough knowledge of neurotransmitters is not only essential for the understanding of the clock but also for the successful manipulation of the clock with experimental chemicals and therapeutical drugs. This article reviews the current knowledge about neurotransmitters in the SCN, including neurotransmitters that have been identified only recently. An attempt was made to describe the neurotransmitters and hormonal/diffusible signals of the SCN efference, which are necessary for the master clock to exert its overt function. The expression of robust circadian rhythms depends on the integrity of the biological clock and on the integration of thousands of individual cellular clocks found in the clock. Neurotransmitters are required at all levels, at the input, in the clock itself, and in its efferent output for the normal function of the clock. The relationship between neurotransmitter function and gene expression is also discussed because clock gene transcription forms the molecular basis of the clock and its working. PMID:16480518

  6. Separating Cloud Forming Nuclei from Interstitial Aerosol

    SciTech Connect

    Kulkarni, Gourihar R.

    2012-09-12

    It has become important to characterize the physicochemical properties of aerosol that have initiated the warm and ice clouds. The data is urgently needed to better represent the aerosol-cloud interaction mechanisms in the climate models. The laboratory and in-situ techniques to separate precisely the aerosol particles that act as cloud condensation nuclei (CCN) and ice nuclei (IN), termed as cloud nuclei (CN) henceforth, have become imperative in studying aerosol effects on clouds and the environment. This review summarizes these techniques, design considerations, associated artifacts and challenges, and briefly discusses the need for improved designs to expand the CN measurement database.

  7. Beta-delayed fission probabilities of transfermium nuclei, involved in the r-process

    NASA Astrophysics Data System (ADS)

    Panov, I.; Lutostansky, Yu; Thielemann, F.-K.

    2016-01-01

    For the nucleosynthesis of heavy and superheavy nuclei fission becomes very important when the r-process runs in a very high neutron density environment. In part, fission is responsible for the formation of heavy nuclei due to the inclusion of fission products as new seed nuclei (fission cycling). More than that, beta-delayed fission, along with spontaneous fission, is responsible in the late stages of the r-process for the suppression of superheavy element yields. For beta-delayed fission probability calculations a model description of the beta-strength- functions is required. Extended theoretical predictions for astro-physical applications were provided long ago, and new predictions also for superheavy nuclei with uptodate nuclear input are needed. For the further extension of data to heavier transactinides the models of strength- functions should be modified, taking into account more complicated level schemes. In our present calculations the strength-function model is based on the quasi-particle approximation of Finite Fermi Systems Theory. The probabilities of beta-delayed fission and beta-delayed neutron emission are calculated for some transfermium neutron-rich nuclei, and the influence of beta-delayed fission upon superheavy element formation is discussed.

  8. Downscaling the environmental associations and spatial patterns of species richness.

    PubMed

    Keil, Petr; Jetz, Walter

    2014-06-01

    We introduce a method that enables the estimation of species richness environment association and prediction of geographic patterns of species richness at grains finer than the original grain of observation. The method is based on a hierarchical model that uses coarse-grain values of species richness and fine-grain environmental data as input. In the model, the (unobserved) fine-grain species richness is linked to the observed fine-grain environment and upscaled using a simple species-area relationship (SAR). The upscaled values are then stochastically linked to the observed coarse-grain species richness. We tested the method on Southern African Bird Atlas data by downscaling richness from 2 degrees to 0.25 degrees (-250 km to -30 km) resolution. When prior knowledge of the SAR slope (average species turnover within coarse-grain cells) was available, the method predicted the fine-grain relationship between richness and environment and provided fine-grain predictions of richness that closely resembled results from native fine-grain models. Without the SAR knowledge the method still accurately quantified the richness-environment relationship, but accurately predicted only relative (rank) values of richness. The approach can be easily extended and it is a powerful path for cross-scale statistical modeling of richness-environment relationships, and for the provision of high-resolution maps for basic science and conservation.

  9. Elastic scattering, fusion, and breakup of light exotic nuclei

    NASA Astrophysics Data System (ADS)

    Kolata, J. J.; Guimarães, V.; Aguilera, E. F.

    2016-05-01

    The present status of fusion reactions involving light ( A < 20) radioactive projectiles at energies around the Coulomb barrier ( E < 10 MeV per nucleon) is reviewed, emphasizing measurements made within the last decade. Data on elastic scattering (providing total reaction cross section information) and breakup channels for the involved systems, demonstrating the relationship between these and the fusion channel, are also reviewed. Similarities and differences in the behavior of fusion and total reaction cross section data concerning halo nuclei, weakly-bound but less exotic projectiles, and strongly-bound systems are discussed. One difference in the behavior of fusion excitation functions near the Coulomb barrier seems to emerge between neutron-halo and proton-halo systems. The role of charge has been investigated by comparing the fusion excitation functions, properly scaled, for different neutron- and proton-rich systems. Possible physical explanations for the observed differences are also reviewed.

  10. Cerenkov counters for high energy nuclei: Some new developments

    NASA Technical Reports Server (NTRS)

    Swordy, S. P.; Muller, D.

    1985-01-01

    A method to determine with gas Cerenkov counters the Lorentz factor, gamma = E/mc, of cosmic ray nuclei with high accuracy over the range gamma approx. 20 to 100 is discussed. The measurement of the Cerenkov emission angle theta, by use of a suitable imaging system is considered. Imaging counters, the ring imaging Cerenkov counters (RICH), were developed for use on accelerators. The image of off-axis particles to determine the amount of image distortion as a function of the direction of the incoming nucleus is examined and an acceptance solid angle, relative to the optical axis, within which the nucleus produces an image with an acceptable level of distortion is defined. The properties of the image, which becomes elliptical, for off-axis particles are analyzed.

  11. Study of multi-nucleon transfer reactions with light nuclei

    SciTech Connect

    Benzoni, G.; Montanari, D.; Bracco, A.; Blasi, N.; Camera, F.; Crespi, F. C. L.; Corsi, A.; Leoni, S.; Million, B.; Nicolini, R.; Wieland, O.; Zalite, A.; Zocca, F.; Azaiez, F.; Franchoo, S.; Stefan, I.; Ibrahim, F.; Verney, D.; Battacharyya, S.; De France, G.

    2008-05-12

    Multi-nucleon transfer reactions are useful tools to populate exotic nuclei, particularly the neutron-rich ones. In this view, two different experiments have been performed employing a stable ({sup 22}Ne) and a radioactive ({sup 24}Ne) beam, both impinging on a {sup 208}Pb target. The first reaction has been studied using the CLARA-PRISMA-DANTE set-up at Laboratori Nazionali di Legnaro (Legnaro-Italy), while the second reaction was performed at Ganil (Caen-France) employing a SPIRAL radioactive beam of {sup 24}Ne. In this case recoils and coincident {gamma} rays were detected with the VAMOS-EXOGAM set-up.The data show that MNT reactions can selectively populate states of different nature and, therefore, are a good tool to study nuclear structure further away from stability.

  12. Odd-even staggering in neutron drip line nuclei

    NASA Astrophysics Data System (ADS)

    Changizi, S. A.; Qi, Chong

    2016-07-01

    We have done systematic Hartree-Fock-Bogoliubov calculations in coordinate space on the one-quasi-particle energies and binding energy odd-even staggering (OES) in semi-magic nuclei with the zero-range volume, mixed and surface pairing forces in order to explore the influence of their density dependence. The odd-N isotopes are calculated within the blocking scheme. The strengths for the pairing forces are determined in two schemes by fitting locally to reproduce pairing gap in 120Sn and globally to all available data on the OES of semi-magic nuclei with Z ≥ 8. In the former calculations, there is a noticeable difference between the neutron mean gaps in neutron-rich O, Ca, Ni and Sn isotopes calculated with the surface pairing and those with the mixed and volume pairing. The difference gets much smaller if the globally optimized pairing strengths are employed. The heavier Pb isotopes show the opposite trend. Moreover, large differences between the mean gap and the OES may be expected in both calculations when one goes towards the neutron drip line.

  13. ULTRA-RELATIVISTIC NUCLEI: A NEW FRONTIER

    SciTech Connect

    MCLERRAN,L.

    1999-10-29

    The collisions of ultra-relativistic nuclei provide a window on the behavior of strong interactions at asymptotically high energies. They also will allow the authors to study the bulk properties of hadronic matter at very high densities.

  14. GDR in Hot Nuclei: New Measurements

    NASA Astrophysics Data System (ADS)

    Camera, F.; Kmiecik, M.; Wieland, O.; Benzoni, G.; Bracco, A.; Brambilla, S.; Crespi, F.; Mason, P.; Moroni, A.; Million, B.; Leoni, S.; Maj, A.; Styczen, J.; Brekiesz, M.; Meczynski, W.; Zieblinski, M.; Gramegna, F.; Barlini, S.; Kravchuk, V. L.; Lanchais, A. L.; Mastinu, P. F.; Bruno, M.; D'Agostino, M.; Geraci, E.; Ordine, A.; Casini, G.; Chiari, M.

    2005-04-01

    The measured properties of the Giant Dipole Resonance in hot rotating nuclei are successfully described with the model of thermal fluctuations, even though there are still some open problems especially at very low (T < 1.2MeV), very high (T >2.5MeV) temperatures and missing data in some mass regions. Recent experimental works have addressed more specific problems regarding the nuclear shape and its behaviour in very particular and delimited phase space regions. In this paper will be discussed new exclusive measurements of the GDR γ decay in heavy 216Rn nuclei (where the shape of nuclei surviving fission have been probed) and some preliminary data on the 132Ce nuclei at very high excitation energy.

  15. Clusterization and quadrupole deformation in nuclei

    SciTech Connect

    Cseh, J.; Algora, A.; Antonenko, N. V.; Jolos, R. V.; Scheid, W.; Darai, J.; Hess, P. O.

    2006-04-26

    We study the interrelation of the clusterization and quadrupole deformation of atomic nuclei, by applying cluster models. Both the energetic stability and the exclusion principle is investigated. Special attention is paid to the relative orientations of deformed clusters.

  16. From Nucleons To Nuclei To Fusion Reactions

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R; Horiuchi, W

    2012-02-15

    Nuclei are prototypes of many-body open quantum systems. Complex aggregates of protons and neutrons that interact through forces arising from quantum chromo-dynamics, nuclei exhibit both bound and unbound states, which can be strongly coupled. In this respect, one of the major challenges for computational nuclear physics, is to provide a unified description of structural and reaction properties of nuclei that is based on the fundamental underlying physics: the constituent nucleons and the realistic interactions among them. This requires a combination of innovative theoretical approaches and high-performance computing. In this contribution, we present one of such promising techniques, the ab initio no-core shell model/resonating-group method, and discuss applications to light nuclei scattering and fusion reactions that power stars and Earth-base fusion facilities.

  17. A focus on shape coexistence in nuclei

    NASA Astrophysics Data System (ADS)

    Wood, J. L.; Heyde, K.

    2016-02-01

    The present collection of articles focuses on new directions and developments under the title of shape coexistence in nuclei, following our 2011 Reviews of Modern Physics article (K Heyde and J L Wood).

  18. Understanding nuclei in the upper sd - shell

    SciTech Connect

    Sarkar, M. Saha; Bisoi, Abhijit; Ray, Sudatta; Kshetri, Ritesh; Sarkar, S.

    2014-08-14

    Nuclei in the upper-sd shell usually exhibit characteristics of spherical single particle excitations. In the recent years, employment of sophisticated techniques of gamma spectroscopy has led to observation of high spin states of several nuclei near A ≃ 40. In a few of them multiparticle, multihole rotational states coexist with states of single particle nature. We have studied a few nuclei in this mass region experimentally, using various campaigns of the Indian National Gamma Array setup. We have compared and combined our empirical observations with the large-scale shell model results to interpret the structure of these nuclei. Indication of population of states of large deformation has been found in our data. This gives us an opportunity to investigate the interplay of single particle and collective degrees of freedom in this mass region.

  19. Perspectives of production of superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Adamian, G. G.; Antonenko, N. V.; Bezbakh, A. N.; Sargsyan, V. V.; Scheid, W.

    2016-07-01

    Possible ways of production of superheavies are discussed. Impact of nuclear structure on the production of superheavy nuclei in complete fusion reactions is discussed. The proton shell closure at Z = 120 is discussed.

  20. Infrared Observations of Cometary Dust and Nuclei

    NASA Technical Reports Server (NTRS)

    Lisse, Carey

    2004-01-01

    This bibliography lists citations for publications published under the grant. Subjects of the publications include cometary dust, instellar and interplanetary dust, comet nuclei and comae, Comet Hale-Bopp, infrared observations of comets, mass loss, and comet break-up.

  1. Organization of projections from the raphe nuclei to the vestibular nuclei in rats

    NASA Technical Reports Server (NTRS)

    Halberstadt, A. L.; Balaban, C. D.

    2003-01-01

    Previous anatomic and electrophysiological evidence suggests that serotonin modulates processing in the vestibular nuclei. This study examined the organization of projections from serotonergic raphe nuclei to the vestibular nuclei in rats. The distribution of serotonergic axons in the vestibular nuclei was visualized immunohistochemically in rat brain slices using antisera directed against the serotonin transporter. The density of serotonin transporter-immunopositive fibers is greatest in the superior vestibular nucleus and the medial vestibular nucleus, especially along the border of the fourth ventricle; it declines in more lateral and caudal regions of the vestibular nuclear complex. After unilateral iontophoretic injections of Fluoro-Gold into the vestibular nuclei, retrogradely labeled neurons were found in the dorsal raphe nucleus (including the dorsomedial, ventromedial and lateral subdivisions) and nucleus raphe obscurus, and to a minor extent in nucleus raphe pallidus and nucleus raphe magnus. The combination of retrograde tracing with serotonin immunohistofluorescence in additional experiments revealed that the vestibular nuclei receive both serotonergic and non-serotonergic projections from raphe nuclei. Tracer injections in densely innervated regions (especially the medial and superior vestibular nuclei) were associated with the largest numbers of Fluoro-Gold-labeled cells. Differences were observed in the termination patterns of projections from the individual raphe nuclei. Thus, the dorsal raphe nucleus sends projections that terminate predominantly in the rostral and medial aspects of the vestibular nuclear complex, while nucleus raphe obscurus projects relatively uniformly throughout the vestibular nuclei. Based on the topographical organization of raphe input to the vestibular nuclei, it appears that dense projections from raphe nuclei are colocalized with terminal fields of flocculo-nodular lobe and uvula Purkinje cells. It is hypothesized that

  2. Cosmic Ray Nuclei (CRN) detector investigation

    NASA Technical Reports Server (NTRS)

    Meyer, Peter; Muller, Dietrich; Lheureux, Jacques; Swordy, Simon

    1991-01-01

    The Cosmic Ray Nuclei (CRN) detector was designed to measure elemental composition and energy spectra of cosmic radiation nuclei ranging from lithium to iron. CRN was flown as part of Spacelab 2 in 1985, and consisted of three basic components: a gas Cerenkov counter, a transition radiation detector, and plastic scintillators. The results of the experiment indicate that the relative abundance of elements in this range, traveling at near relativistic velocities, is similar to those reported at lower energy.

  3. Recent results at ultrahigh spin: Terminating states and beyond in mass 160 rare-earth nuclei

    DOE PAGES

    Paul, E. S.; Rees, J. M.; Hampson, P.; Riley, M. A.; Simpson, J.; Ayangeakaa, A. D.; Baron, J. S.; Carpenter, M. P.; Chiara, C. J.; Garg, U.; et al

    2015-01-01

    A classic region of band termination at high spin occurs in rare-earth nuclei with around ten valence nucleons above the 146Gd closed core. The results are presented here for such non-collective oblate (γ = 60°) terminating states in odd-Z 155Ho, odd–odd 156Ho, and even–even 156Er, where they are compared with neighboring nuclei. In addition to these particularly favoured states, the occurrence of collective triaxial strongly deformed (TSD) bands, bypassing the terminating states and extending to over 65ℏ, is reviewed.

  4. Time-dependent Hartree-Fock Study of Octupole Vibrations in doubly magic nuclei

    NASA Astrophysics Data System (ADS)

    Simenel, C.; Buete, J.; Vo-Phuoc, K.

    2016-09-01

    Octupole vibrations are studied in some doubly magic nuclei using the time-dependent Hartree-Fock (TDHF) theory with a Skyrme energy density functional. Through the use of the linear response theory, the energies and transition amplitudes of the low-lying vibrational modes for each of the nuclei were determined. Energies were found to be close to experimental results. However, transition amplitudes, quantified by the deformation parameter β3, are underestimated by TDHF. A comparison with single-particle excitations on the Hartree-Fock ground-state shows that the collective octupole vibrations have their energy lowered due to attractive RPA residual interaction.

  5. Recent results at ultrahigh spin: Terminating states and beyond in mass 160 rare-earth nuclei

    SciTech Connect

    Paul, E. S.; Rees, J. M.; Hampson, P.; Riley, M. A.; Simpson, J.; Ayangeakaa, A. D.; Baron, J. S.; Carpenter, M. P.; Chiara, C. J.; Garg, U.; Hartley, D. J.; Hoffman, C. R.; Janssens, R. V. F.; Kondev, F. G.; Lauritsen, T.; Mason, P. J. R.; Matta, J.; Miller, S. L.; Nolan, P. J.; Ollier, J.; Petri, M.; Radford, D. C.; Revill, J. P.; Wang, X.; Zhu, S.; Ragnarsson, I.

    2015-01-01

    A classic region of band termination at high spin occurs in rare-earth nuclei with around ten valence nucleons above the 146Gd closed core. The results are presented here for such non-collective oblate (γ = 60°) terminating states in odd-Z 155Ho, odd–odd 156Ho, and even–even 156Er, where they are compared with neighboring nuclei. In addition to these particularly favoured states, the occurrence of collective triaxial strongly deformed (TSD) bands, bypassing the terminating states and extending to over 65ℏ, is reviewed.

  6. Conservation of Isospin in Neutron-rich Fission Fragments

    SciTech Connect

    Jain, A.K.; Choudhury, D.; Maheshwari, B.

    2014-06-15

    On the occasion of the 75{sup th} anniversary of the fission phenomenon, we present a surprisingly simple result which highlights the important role of isospin and its conservation in neutron rich fission fragments. We have analysed the fission fragment mass distribution from two recent heavyion reactions {sup 238}U({sup 18}O,f) and {sup 208}Pb({sup 18}O,f) as well as a thermal neutron fission reaction {sup 245}Cm(n{sup th},f). We find that the conservation of the total isospin explains the overall trend in the observed relative yields of fragment masses in each fission pair partition. The isospin values involved are very large making the effect dramatic. The findings open the way for more precise calculations of fission fragment distributions in heavy nuclei and may have far reaching consequences for the drip line nuclei, HI fusion reactions, and calculation of decay heat in the fission phenomenon.

  7. Conservation of Isospin in Neutron-rich Fission Fragments

    NASA Astrophysics Data System (ADS)

    Jain, A. K.; Choudhury, D.; Maheshwari, B.

    2014-06-01

    On the occasion of the 75th anniversary of the fission phenomenon, we present a surprisingly simple result which highlights the important role of isospin and its conservation in neutron rich fission fragments. We have analysed the fission fragment mass distribution from two recent heavyion reactions 238U(18O,f) and 208Pb(18O,f) as well as a thermal neutron fission reaction 245Cm(nth,f). We find that the conservation of the total isospin explains the overall trend in the observed relative yields of fragment masses in each fission pair partition. The isospin values involved are very large making the effect dramatic. The findings open the way for more precise calculations of fission fragment distributions in heavy nuclei and may have far reaching consequences for the drip line nuclei, HI fusion reactions, and calculation of decay heat in the fission phenomenon.

  8. The effects of the local environment on active galactic nuclei

    SciTech Connect

    Manzer, L. H.; De Robertis, M. M. E-mail: mmdr@yorku.ca

    2014-06-20

    There continues to be significant controversy regarding the mechanism(s) responsible for the initiation and maintenance of activity in galactic nuclei. In this paper we will investigate possible environmental triggers of nuclear activity through a statistical analysis of a large sample of galaxy groups. The focus of this paper is to identify active galactic nuclei (AGNs) and other emission-line galaxies in these groups and to compare their frequency with a sample of over 260,000 isolated galaxies from the same catalog. The galaxy groups are taken from the catalog of Yang et al., in which over 20,000 virialized groups of galaxies (2 ≤ N ≤ 20) with redshifts between 0.01 and 0.20 are from the Sloan Digital Sky Survey. We first investigate the completeness of our data set and find, though biases are a concern particularly at higher redshift, that our data provide a fair representation of the local universe. After correcting emission-line equivalent widths for extinction and underlying Balmer stellar absorption, we classify galaxies in the sample using traditional emission-line ratios, while incorporating measurement uncertainties. We find a significantly higher fraction of AGNs in groups compared with the isolated sample. Likewise, a significantly higher fraction of absorption-line galaxies are found in groups, while a higher fraction of star-forming galaxies prefer isolated environments. Within grouped environments, AGNs and star-forming galaxies are found more frequently in small- to medium-richness groups, while absorption-line galaxies prefer groups with larger richnesses. Groups containing only emission-line galaxies have smaller virial radii, velocity dispersions, and masses compared with those containing only absorption-line galaxies. Furthermore, the AGN fraction increases with decreasing distance to the group centroid, independent of galaxy morphology. Using properties obtained from Galaxy Zoo, there is an increased fraction of AGNs within merging systems

  9. Data Rich, Information Poor

    SciTech Connect

    Kaplan, P.G.; Rautman, C.A.

    1998-11-09

    Surviving in a data-rich environment means understanding the difference between data and information. This paper reviews an environmental case study that illustrates that understanding and shows its importance. In this study, a decision problem was stated in terms of au economic-objective fimction. The function contains a term that defines the stochastic relationship between the decision and the information obtained during field chamctetition for an environmental contaminant. Data is defied as samples drawn or experimental realizations of a mudom fimction. Information is defined as the quantitative change in the value of the objective fiction as a result of the sample.

  10. 76 FR 63702 - In the Matter of the Designation of Conspiracy of Fire Nuclei, aka Conspiracy of the Nuclei of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-13

    ... Matter of the Designation of Conspiracy of Fire Nuclei, aka Conspiracy of the Nuclei of Fire, aka Conspiracy of Cells of Fire, aka Synomosia of Pyrinon Tis Fotias, aka Thessaloniki-Athens Fire Nuclei... January 23, 2003, I hereby determine that the organization known as Conspiracy of Fire Nuclei, also...

  11. Shape Coexistence in Pb-Rn Nuclei Studied by Particle Decay Spectroscopy

    SciTech Connect

    Andreyev, A. N.

    2006-08-14

    This contribution reviews the results of recent experiments at the velocity filter SHIP (GSI, Darmstadt) in which a number of very neutron-deficient nuclei with Z=83-88 and N< 126 were studied in detail and new nuclides 186,187Po, 192At and 193,194Rn were identified. Complete fusion reactions at beam energies close to the Coulomb barrier were used, followed by particle detection with various detection systems. Peculiarities in {alpha}-decay characteristics of the 186-191Po isotopes are discussed in detail. Very recent results for the neutron-deficient At-Ra nuclei from the gas-filled separator RITU (JYFL, Jyvaeskylae) are also highlighted.The application of a new method to reach nuclei in this region - spallation-evaporation reactions of 238U ions at 1 AGeV on a Be target, followed by the separation with the FRS at GSI is discussed as well.

  12. Shape Coexistence in Pb-Rn Nuclei Studied by Particle Decay Spectroscopy

    NASA Astrophysics Data System (ADS)

    Andreyev, A. N.

    2006-08-01

    This contribution reviews the results of recent experiments at the velocity filter SHIP (GSI, Darmstadt) in which a number of very neutron-deficient nuclei with Z=83-88 and N< 126 were studied in detail and new nuclides 186,187Po, 192At and 193,194Rn were identified. Complete fusion reactions at beam energies close to the Coulomb barrier were used, followed by particle detection with various detection systems. Peculiarities in α-decay characteristics of the 186-191Po isotopes are discussed in detail. Very recent results for the neutron-deficient At-Ra nuclei from the gas-filled separator RITU (JYFL, Jyväskylä) are also highlighted. The application of a new method to reach nuclei in this region — spallation-evaporation reactions of 238U ions at 1 AGeV on a Be target, followed by the separation with the FRS at GSI is discussed as well.

  13. Deformation and its influence on K isomerism in neutron-rich Hf nuclei

    SciTech Connect

    Liu, H. L.; Bertulani, C. A.; Xu, F. R.; Walker, P. M.

    2011-06-15

    We investigate the influence of deformation on the possible occurrence of long-lived K isomers in Hf isotopes around N=116, using configuration-constrained calculations of potential-energy surfaces. Despite having reduced shape elongation, the multiquasiparticle states in {sup 186,188}Hf remain moderately robust against triaxial distortion, supporting the long expected occurrence of exceptionally long-lived isomers. The calculations are compared with available experimental data.

  14. Fission barriers for neutron-rich nuclei by means of Skyrme-Hartree-Fock-Bogoliubov calculation

    SciTech Connect

    Hashizume, K.; Wada, T.; Ohta, M.; Samyn, M.; Goriely, S.

    2007-02-26

    The nuclear fission barrier height has been estimated by means of the constraint Skyrme Hartree-Fock-Bogoliubov method. The potential energy surfaces obtained by the method are analyzed with the flooding method to find several saddle points. The results for U, Np, Bk isotopes are compared with the barrier derived from the extended Thomas-Fermi plus Strutinsky integral method.

  15. Structural Evolution in the Neutron-Rich Nuclei {sup 106}Zr and {sup 108}Zr

    SciTech Connect

    Sumikama, T.; Yoshinaga, K.; Miyashita, Y.; Sugimoto, K.; Chiba, J.; Nakano, T.; Takano, S.; Watanabe, H.; Nishimura, S.; Li, Z.; Baba, H.; Doornenbal, P.; Isobe, T.; Kurata-Nishimura, M.; Sakurai, H.; Scheit, H.; Steppenbeck, D.; Yamaguchi, K.; Berryman, J. S.; Blasi, N.

    2011-05-20

    The low-lying states in {sup 106}Zr and {sup 108}Zr have been investigated by means of {beta}-{gamma} and isomer spectroscopy at the radioactive isotope beam factory (RIBF), respectively. A new isomer with a half-life of 620{+-}150 ns has been identified in {sup 108}Zr. For the sequence of even-even Zr isotopes, the excitation energies of the first 2{sup +} states reach a minimum at N=64 and gradually increase as the neutron number increases up to N=68, suggesting a deformed subshell closure at N=64. The deformed ground state of {sup 108}Zr indicates that a spherical subshell gap predicted at N=70 is not large enough to change the ground state of {sup 108}Zr to the spherical shape. The possibility of a tetrahedral shape isomer in {sup 108}Zr is also discussed.

  16. Triaxial and Triaxial Softness in Neutron Rich ru and pd Nuclei

    NASA Astrophysics Data System (ADS)

    Luo, Y. X.; Hamilton, J. H.; Ramaya, A. V.; Hwang, J. K.; Liu, S. H.; Rasmussen, J. O.; Frauendorf, S.; Ter-Akopian, G. M.; Daniel, A. V.; Oganessian, Yu. Ts.; Zhu, S. J.

    2013-06-01

    The level structures of 108,110,112Ru (Z=44) and 112,114,115,116,117,118Pd (Z=46) have been significantly expanded through studies of prompt γ-γ-γ coincidences observed with Gammasphere following the spontaneous fission of 252Cf. The softness to triaxiality perturbs the band structures of 108Ru and even-N Pd isotopes. Two sets of odd-parity bands are identified in 112,114,116Pd similar to but different from those in 110,112Ru. These differences can be accounted for by interferences of the chiral doubling and softness to triaxiality. Also in 112Ru, evidence for wobbling motion is found in the behavior of the γ vibrational band. Similar evidence for wobbling motion is found in 114Pd, the N = 68 isotone of 112Ru.

  17. Single-Neutron Structure of Neutron-Rich Nuclei near N=50 and N=82

    SciTech Connect

    Cizewski, J. A.; Jones, K. L.; Kozub, R. L.; Pain, S. D.; Bardayan, Daniel W; Blackmon, Jeff C; Adekola, Aderemi S; Chae, K. Y.; Chipps, K.; Erikson, Luke; Gaddis, A. L.; Harlin, Christopher W; Hatarik, Robert; Howard, Joshua A; Kaplan, Ron; Krolas, W.; Liang, J Felix; Livesay, Jake; Ma, Zhanwen; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D; O'Malley, Patrick; Patterson, N. P.; Paulauskas, Stanley; Shapira, Dan; Shriner, Jr., John F; Sissom, D. J.; Smith, Michael Scott; Swan, T. P.; Thomas, J. S.; Wilson, Gemma L

    2009-01-01

    The 82Ge, 84Se, 132Sn, 130Sn, and 134Te (d,p) reactions have been measured with {approx}4-5-MeV-A rare isotope beams and CD2 targets at the HRIBF at ORNL. Energies and spectroscopic strengths have been measured for excitations in 83Ge and 85Se. Direct neutron capture calculations on 82Ge are presented. Preliminary results for single-neutron excitations in 131Sn, 133Sn, and 135Te are reported.

  18. Nuclear Shape And Size Properties For Rare-earth Neutron-rich Nuclei

    SciTech Connect

    Benhamouda, N.; Oudih, M. R.; Allal, N. H.; Fellah, M.

    2009-01-28

    Two-neutron separation energies, quadrupole moments and mean square charge radii, are evaluated for even-even Osmium isotopes with 78{<=}N{<=}114. The calculations are performed in the framework of a microscopic model including the pairing correlations rigorously by means of the FSBCS (Fixed-Sharp-BCS) method.

  19. Beta-delayed multi-particle emission in proton rich nuclei

    NASA Astrophysics Data System (ADS)

    Borge, M. J. G.; Axelsson, L.; Äystö, J.; Bergmann, U. C.; Boutami, R.; Deendoven, P.; Fraile, L. M.; Fynbo, H. O. U.; Honkanen, A.; Hornshøj, P.; Huikari, J.; Jokinen, A.; Jonson, B.; Markenroth, K.; Martel, I.; Mukha, I.; Nilsson, T.; Nyman, G.; Oinonen, M.; Prezado, Y.; Riisager, K.; Tengblad, O.; Rolander, K. Wilhelmsen

    2002-04-01

    In this contribution examples of the application of new technologies to disentangle the mechanism of beta-delayed multi-particle emission are given. In particular the mechanism of β-delayed two-proton emission from 31Ar is resolved and proved to be sequential, both for isospin allowed and isospin forbidden transitions. The analysis of the 9C decay has been focused in the study of the 12.2 MeV state in 9B. The decay of this state to pαα occurs sequentially, partial decay branches through the 8Be(0+,2+) and 5Li(3/2-,1/2-) intermediate states have been determined. A BGT value of 1.20(15) is deduced, compared with the BGT-value of the mirror transition, a asymmetry factor δ=3.7(12) is obtained, the largest ever observed. A preview of β3α data from 12N decay is discussed. .

  20. Shape evolution in neutron-rich nuclei near the r-process path

    SciTech Connect

    Wu, Ching-Yen

    2015-10-01

    To assess the resources needed to field a quantitative measurement to advance our knowledge on shape evolution, we have carried out a numerical simulation of the Coulomb excitation for 112Ru at 460 MeV bombarding energy on a 208Pb target of 1 mg/cm2 using a semiclassical code, GOSIA with GRETINA/CHICO2.

  1. Role of nuclear couplings in the inelastic excitation of weakly-bound neutron-rich nuclei

    SciTech Connect

    Dasso, C.H.; Lenzi, S.M.; Vitturi, A.

    1996-12-31

    Much effort is presently devoted to the study of nuclear systems far from the stability line. Particular emphasis has been placed in light systems such as {sup 11}Li, {sup 8}B and others, where the very small binding energy of the last particles causes their density distribution to extend considerably outside of the remaining nuclear core. Some of the properties associated with this feature are expected to characterize also heavier systems in the vicinity of the proton or neutron drip lines. It is by now well established that low-lying concentrations of multipole strength arise from pure configurations in which a peculiar matching between the wavelength of the continuum wavefunction of the particles and the range of the weakly-bound hole states occurs. To this end the authors consider the break-up of a weakly-bound system in a heavy-ion collision and focus attention in the inelastic excitation of the low-lying part of the continuum. They make use of the fact that previous investigations have shown that the multipole response in this region is not of a collective nature and describe their excited states as pure particle-hole configurations. Since the relevant parameter determining the strength distributions is the binding energy of the last bound orbital they find it most convenient to use single-particle wavefunctions generated by a sperical square-well potential with characteristic nuclear dimensions and whose depth has been adjusted to give rise to a situation in which the last occupied neutron orbital is loosely-bound. Spin-orbit couplings are, for the present purpose, ignored. The results of this investigation clearly indicate that nuclear couplings have the predominant role in causing projectile dissociation in many circumstances, even at bombarding energies remarkably below the Coulomb barrier.

  2. Structures of the neutron-rich nuclei observed in fission of {sup 252}Cf

    SciTech Connect

    Ramayya, A. V.; Hamilton, J. H.; Goodin, C. J.; Brewer, N. T.; Hwang, J. K.; Luo, Y. X.; Liu, S. H.; Stone, N. J.; Daniel, A. V.; Zhu, S. J.

    2014-08-14

    Analysis of high statistics triple coincidence fission γ data from {sup 252}Cf at Gammasphere including angular correlations yielded well-expanded high-spin level schemes with more complete and reliable spin/parity assignments for {sup 82}Ge, {sup 118,120,122}Cd and {sup 114,115}Rh. Both the quasi-particle/hole couplings and quasi-rotational degrees of freedom are implied to play roles in these Cd isotopes. Evidence for triaxial shapes and octupole components in the Cd isotopes is presented. These Cd isotopes may have triaxial deformations. High-spin level schemes of {sup 114,115}Rh have been established for the first time. The existence of a relatively large signature splitting and an yrare band shows typical features of a triaxially deformed nucleus. Possible excited deformed rotational bands are observed, for the first time, in {sup 82}Ge. From the multipole mixing ratio measurement, the ground state configurations of {sup 109,111}Ru, as well as excited states in {sup 103,107}Mo and {sup 111}Ru were determined.

  3. Decay Studies of Very Neutron Rich Nuclei near 78Ni

    SciTech Connect

    Winger, J. A.; Ilyushkin, S.; Korgul, A.; Gross, Carl J; Rykaczewski, Krzysztof Piotr; Batchelder, J. C.; Goodin, C.; Grzywacz, R.; Hamilton, J. H.; Krolas, W.; Liddick, Sean; Mazzocchi, C.; Nelson, C.; Padgett, Stephen; Piechaczek, A.; Rajabali, M. M.; Shapira, Dan; Zganjar, E. F.

    2008-01-01

    The properties of beta-gamma and beta-delayed neutron emission from 76-79Cu and 83-85Ga were measured at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. Selected results on the decay properties of copper isotopes are briefly presented and discussed.

  4. Descending spinal projections from the rostral gigantocellular reticular nuclei complex.

    PubMed

    Hermann, Gerlinda E; Holmes, Gregory M; Rogers, Richard C; Beattie, Michael S; Bresnahan, Jacqueline C

    2003-01-01

    Electrophysiological and physiological studies have suggested that the ventral medullary gigantocellular reticular nuclei (composed of the gigantocellular ventralis and pars alpha nuclei as well as the adjacent lateral paragigantocellular nucleus; abbreviated Gi-LPGi complex) provide descending control of pelvic floor organs (Mackel [1979] J. Physiol. (Lond.) 294:105-122; Hubscher and Johnson [1996] J. Neurophysiol. 76:2474-2482; Hubscher and Johnson [1999] J. Neurophysiol. 82:1381-1389; Johnson and Hubscher [1998] Neuroreport 9:341-345). Specifically, this complex of paramedian reticular nuclei has been implicated in the inhibition of sexual reflexes. In the present study, an anterograde fluorescent tracer was used to investigate direct descending projections from the Gi-LPGi complex to retrogradely labeled pudendal motoneurons (MN) in the male rat. Our results demonstrated that, although a high density of arborizations from Gi-LPGi fibers appears to be in close apposition to pudendal MNs, this relationship also applies to other MNs throughout the entire spinal cord. The Gi-LPGi also projects to spinal autonomic regions, i.e., both the intermediolateral cell column and the sacral parasympathetic nucleus, as well as to regions of the intermediate gray, which contain interneurons involved in the organization of pelvic floor reflexes. Lastly, throughout the length of the spinal cord, numerous neurons located primarily in laminae VII-X, were retrogradely labeled with Fluoro-Ruby after injections into the Gi-LPGi. The diffuse descending projections and arborizations of this pathway throughout the spinal cord suggest that this brainstem area is involved in the direct, descending control of a variety of spinal activities. These results are in contrast with our observations of the discrete projections of the caudal nucleus raphe obscurus, which target the autonomic and somatic MNs involved specifically in sexual and eliminative functions (Hermann et al. [1998] J. Comp

  5. Spin evolution of supermassive black holes and galactic nuclei

    NASA Astrophysics Data System (ADS)

    Merritt, David; Vasiliev, Eugene

    2012-11-01

    The spin angular momentum S of a supermassive black hole (SBH) precesses due to torques from orbiting stars, and the stellar orbits precess due to dragging of inertial frames by the spinning hole. We solve the coupled post-Newtonian equations describing the joint evolution of S and the stellar angular momenta Lj, j=1…N in spherical, rotating nuclear star clusters. In the absence of gravitational interactions between the stars, two evolutionary modes are found: (1) nearly uniform precession of S about the total angular momentum vector of the system and (2) damped precession, leading, in less than one precessional period, to alignment of S with the angular momentum of the rotating cluster. Beyond a certain distance from the SBH, the time scale for angular momentum changes due to gravitational encounters between the stars is shorter than spin-orbit precession times. We present a model, based on the Ornstein-Uhlenbeck equation, for the stochastic evolution of star clusters due to gravitational encounters and use it to evaluate the evolution of S in nuclei where changes in the Lj are due to frame dragging close to the SBH and to encounters farther out. Long-term evolution in this case is well described as uniform precession of the SBH about the cluster’s rotational axis, with an increasingly important stochastic contribution when SBH masses are small. Spin precessional periods are predicted to be strongly dependent on nuclear properties, but typical values are ˜107-108yr for low-mass SBHs in dense nuclei, ˜108-1010yr for SBH masses ˜108M⊙, and ˜1010-1011yr for the most massive SBHs. We compare the evolution of SBH spins in stellar nuclei to the case of torquing by an inclined, gaseous accretion disk.

  6. Compact Nuclei in Galaxies at Moderate Redshift

    NASA Astrophysics Data System (ADS)

    Sarajedini, Vicki Lynn

    The purpose of this study is to understand the space density and properties of active galaxies to z ≃ 0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged galaxies with multi-component models using maximum likelihood estimate techniques to determine the best model fit. We select those galaxies requiring an unresolved, point source component in the galaxy nucleus, in addition to a disk and/or bulge component, to adequately model the galaxy light. We have searched 70 WFPC2 images primarily from the Medium Deep Survey for galaxies containing compact nuclei. In our survey of 1033 galaxies, the fraction containing an unresolved nuclear component ≥3% of the total galaxy light is 16±3% corrected for incompleteness and 9±1% for nuclei ≥5% of the galaxy light. Most of the nuclei are ~<20% of the total galaxy light. The majority of the host galaxies are spirals with little or no bulge component. The V-I colors of the nuclei are compared with synthetic colors for Seyferts and starburst nuclei to help differentiate between AGNs and starbursts in our sample. Spectroscopic redshifts have been obtained for 35 of our AGN/starburst candidates and photometric redshifts are estimated to an accuracy of σz≃0.1 for the remaining sample. We present the upper limit luminosity function (LF) for low-luminosity AGN (LLAGN) in two redshift bins to z = 0.8. We detect mild number density evolution of the form φ∝ (1+z)1.9 for nuclei at -18 ~

  7. Stability and production of superheavy nuclei

    SciTech Connect

    Moeller, P. |; Nix, J.R.

    1997-12-31

    Beyond uranium heavy elements rapidly become increasingly unstable with respect to spontaneous fission as the proton number Z increases, because of the disruptive effect of the long-range Coulomb force. However, in the region just beyond Z = 100 magic proton and neutron numbers and the associated shell structure enhances nuclear stability sufficient to allow observation of additional nuclei. Some thirty years ago it was speculated that an island of spherical, relatively stable superheavy nuclei would exist near the next doubly magic proton-neutron combination beyond {sup 208}Pb, that is, at proton number Z = 114 and neutron number N = 184. Theory and experiment now show that there also exists a rock of stability in the vicinity of Z = 110 and N = 162 between the actinide region, which previously was the end of the peninsula of known elements, and the predicted island of spherical superheavy nuclei slightly southwest of the magic numbers Z = 114 and N = 184. The authors review here the stability properties of the heavy region of nuclei. Just as the decay properties of nuclei in the heavy region depend strongly on shell structure, this structure also dramatically affects the fusion entrance channel. The six most recently discovered new elements were all formed in cold-fusion reactions. They discuss here the effect of the doubly magic structure of the target in cold-fusion reactions on the fusion barrier and on dissipation.

  8. Synthesis and decay process of superheavy nuclei with Z=119-122 via hot-fusion reactions

    NASA Astrophysics Data System (ADS)

    Ghahramany, N.; Ansari, A.

    2016-09-01

    In this research article attempts have been made to calculate the superheavy-nuclei synthesis characteristics including, the potential energy parameters, fusion probability, fusion and evaporation residue (ER) cross sections as well as, decay properties of compound nucleus and the residue nuclei formation probability for elements with Z=119-122 by using the hot-fusion reactions. It is concluded that, although a selection of double magic projectiles such as 48Ca with high binding energy, simplifies the calculations significantly due to spherical symmetric shape of the projectile, resulting in high evaporation residue cross section, unfortunately, nuclei with Z > 98 do not exist in quantities sufficient for constructing targets for the hot-fusion reactions. Therefore, practically our selection is fusion reactions with titanium projectile because the mass production of target nuclei for experimental purposes is more feasible. Based upon our findings, it is necessary, for new superheavy-nuclei production with Z > 119, to use neutron-rich projectiles and target nuclei. Finally, the maximal evaporation residue cross sections for the synthesis of superheavy elements with Z=119-122 have been calculated and compared with the previously founded ones in the literature.

  9. Comparative analysis of the nucleosome structure of cell nuclei by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Isaev-Ivanov, V. V.; Lebedev, D. V.; Lauter, H.; Pantina, R. A.; Kuklin, A. I.; Islamov, A. Kh.; Filatov, M. V.

    2010-05-01

    The nucleosome structure in native nuclei of normal (chicken erythrocyte and rat leukocyte nuclei) and anomalously proliferating (the human cervical adenocarcinoma cell line HeLa and the Chinese hamster fibroblast cell line A238) cells has been investigated using small-angle neutron scattering. The experimental results obtained allow one to make the inference that the parameters of the nucleosome structure for the chicken erythrocyte and rat leukocyte nuclei (on average over the nucleus) are close to the universally accepted values and that the distance distribution function is bimodal. The bimodality of the distance distribution function reflects a narrow distribution of distances between nucleosomes (on average over the nucleus) at the fibril level of the chromatin organization. The histone core of the nucleosome structure in the nuclei of the HeLa and A238 cells (on average over the nucleus) is considerably less compact than that in the chicken erythrocyte and rat leukocyte nuclei, and the distance distribution function does not exhibit indications of the bimodality.

  10. New high spin states and isomers in the {sup 208}Pb and {sup 207}Pb nuclei

    SciTech Connect

    Broda, R.; Wrzesinski, J.; Pawlat, T.

    1996-12-31

    The two most prominent examples of the heavy doubly closed shell (DCS) nuclei, {sup 208}Pb and {sup 132}Sn, are not accessible by conventional heavy-ion fusion processes populating high-spin states. This experimental difficulty obscured for a long time the investigation of yrast high-spin states in both DCS and neighboring nuclei and consequently restricted the study of the shell model in its most attractive regions. Recent technical development of multidetector gamma arrays opened new ways to exploit more complex nuclear processes which populate the nuclei of interest with suitable yields for gamma spectroscopy and involve population of moderately high spin states. This new possibility extended the range of accessible spin values and is a promising way to reach new yrast states. Some of these states are expected to be of high configurational purity and can be a source of important shell model parameters which possibly can be used later to check the validity of the spherical shell model description at yet higher spin and higher excitation energy. The nuclei in the closest vicinity of {sup 132}Sn are produced in spontaneous fission and states with spin values up to I=14 can be reached in fission gamma spectroscopy studies with the presently achieved sensitivity of gamma arrays. New results on yrast states in the {sup 134}Te and {sup 135}I nuclei populated in fission of the {sup 248}Cm presented at this conference illustrate such application of the resolving power offered by modern gamma techniques.

  11. Cd-rich and Te-rich low-temperature photoluminescence in cadmium telluride

    SciTech Connect

    Albin, D. S. Kuciauskas, D.; Ma, J.; Metzger, W. K.; Burst, J. M.; Moutinho, H. R.; Dippo, P. C.

    2014-03-03

    Low-temperature photoluminescence emission spectra were measured in cadmium telluride (CdTe) samples in which composition was varied to promote either Cd or Te-rich stoichiometry. The ability to monitor stoichiometry is important, since it has been shown to impact carrier recombination. Te-rich samples show transitions corresponding to acceptor-bound excitons (∼1.58 eV) and free-electron to acceptor transitions (∼1.547 eV). In addition to acceptor-bound excitons, Cd-rich samples show transitions assigned to donor-bound excitons (1.591 eV) and Te vacancies at 1.552 eV. Photoluminescence is a noninvasive way to monitor stoichiometric shifts induced by post-deposition anneals in polycrystalline CdTe thin films deposited by close-spaced sublimation.

  12. Subcellular localization of creatine kinase in Torpedo electrocytes: association with acetylcholine receptor-rich membranes

    PubMed Central

    1985-01-01

    Creatine kinase (CK, EC 2.7.3.2) has recently been identified as the intermediate isoelectric point species (pl 6.5-6.8) of the Mr 40,000- 43,000 nonreceptor, peripheral v-proteins in Torpedo marmorata acetylcholine receptor-rich membranes (Barrantes, F. J., G. Mieskes, and T. Wallimann, 1983, Proc. Natl. Acad. Sci. USA, 80: 5440-5444). In the present study, this finding is substantiated at the cellular and subcellular level of the T. marmorata electric organ by immunofluorescence and by protein A-gold labeling of either ultrathin cryosections of electrocytes or purified receptor-membrane vesicles that use subunit-specific anti-chicken creatine kinase antibodies. The muscle form of the kinase, on the one hand, is present throughout the entire T. marmorata electrocyte except in the nuclei. The brain form of the kinase, on the other hand, is predominantly located on the ventral, innervated face of the electrocyte, where it is closely associated with both surfaces of the postsynaptic membrane, and secondarily in the synaptic vesicles at the presynaptic terminal. Labeling of the noninnervated dorsal membrane is observed at the invaginated sac system. In the case of purified acetylcholine receptor-rich membranes, antibodies specific for chicken B-CK label only one face of the isolated vesicles. No immunoreaction is observed with anti-chicken M-CK antibodies. A discussion follows on the possible implications of these localizations of creatine kinase in connection with the function of the acetylcholine receptor at the postsynaptic membrane, the Na/K ATPase at the dorsal electrocyte membrane, and the ATP-dependent transmitter release at the nerve ending. PMID:3884630

  13. Histidine kinase activity in nuclei of Physarum polycephalum

    SciTech Connect

    Matthews, H.R.; Pesis, K. Wei, Y.

    1987-05-01

    Nuclei of the true slime mold Physarum polycephalum, contain a kinase that specifically phosphorylates the 1-nitrogen of histidine-75 of histone H4, in vitro. Phosphohistidine is alkali stable and acid labile. Similar alkali stable phosphorylation has been observed with beef heart extracts and S-100 extracts from S. cerevisiae. The activity may be similar to that previously reported by R.A. Smith and his colleagues in several mammalian tissues. They have begun a search for nuclear proteins that contain phosphohistidine. Cultures of Physarum were grown in the presence of /sup 32/P-phosphate using several different labeling protocols. Labeled nuclear proteins were fractionated on a Superose-12 column. Alkali stable phosphate label eluted close to the position of histone H1, although it was not on H1 itself. No alkali stable phosphate eluted at the position of histone H4, which was obtained in high yield by this procedure. The absence of alkali-stable phosphorylation of histone H4 was confirmed by gel electrophoresis of the crude nuclear proteins. The fraction containing alkali-stable phosphate was shown to contain phosphohistidine by amino acid analysis of a total alkaline hydrolysate. They conclude that Physarum nuclei possess at least one protein that contains phosphohistidine in vivo and that histone H4 does not contain phosphohistidine in this system.

  14. Magnetic moments of light nuclei from lattice quantum chromodynamics

    SciTech Connect

    Beane, S.  R.; Chang, E.; Cohen, S.; Detmold, W.; Lin, H.  W.; Orginos, K.; Parreño, A.; Savage, M.  J.; Tiburzi, B.  C.

    2014-12-16

    We present the results of lattice QCD calculations of the magnetic moments of the lightest nuclei, the deuteron, the triton and 3He, along with those of the neutron and proton. These calculations, performed at quark masses corresponding to mπ ~ 800 MeV, reveal that the structure of these nuclei at unphysically heavy quark masses closely resembles that at the physical quark masses. We find that the magnetic moment of 3He differs only slightly from that of a free neutron, as is the case in nature, indicating that the shell-model configuration of two spin-paired protons and a valence neutron captures its dominant structure. Similarly a shell-model-like moment is found for the triton, μ3H ~ μp. The deuteron magnetic moment is found to be equal to the nucleon isoscalar moment within the uncertainties of the calculations.

  15. Structure and spectroscopy of transcurium nuclei.

    SciTech Connect

    Ahmad, I.

    2001-11-09

    The stability of the superheavy elements depends on the shell corrections which are governed by the single-particle spectra. Ideally one would like to experimentally determine the single-particle levels in the superheavy nuclei but the production of only a few atoms of these nuclides precludes such measurements. One therefore has to identify single-particle levels in the heaviest nuclei which are available in at least nanoCurie amounts. They have studied the structure of such heavy nuclei in the Z=98 region and identified many single-particle states. In particular, they have studied the structure of {sup 251}Cf and {sup 249}Bk by measuring the radiations emitted in the {alpha} decay of {sup 255}Fm and {sup 253}Es. These single-particle spectra can be used to test theoretical models for superheavy elements.

  16. Is Fusion Inhibited for Weakly Bound Nuclei?

    SciTech Connect

    Takahashi, J.; Munhoz, M.; Szanto, E.M.; Carlin, N.; Added, N.; Suaide, A.A.; de Moura, M.M.; Liguori Neto, R.; Szanto de Toledo, A.; Canto, L.F.

    1997-01-01

    Complete fusion of light radioactive nuclei is predicted to be hindered at near-barrier energies. This feature is investigated in the case of the least bound stable nuclei. Evaporation residues resulting from the {sup 6,7}Li+{sup 9}Be and {sup 6,7}Li+{sup 12}C fusion reactions have been measured in order to study common features in reactions involving light weakly bound nuclei. The experimental excitation functions revealed that the fusion cross section is significantly smaller than the total reaction cross section and also smaller than the fusion cross section expected from the available systematics. A clear correlation between the fusion probability and nucleon (cluster) separation energy has been established.The results suggest that the breakup process has a strong influence on the hindrance of the fusion cross section. {copyright} {ital 1996} {ital The American Physical Society}

  17. Automatic Segmentation of Cell Nuclei in Bladder and Skin Tissue for Karyometric Analysis

    PubMed Central

    Korde, Vrushali R.; Bartels, Hubert; Barton, Jennifer; Ranger-Moore, James

    2010-01-01

    Objective To automatically segment cell nuclei in histology images of bladder and skin tissue for karyometric analysis. Study Design The four main steps in the program were as follows: median filtering and thresholding, segmentation, categorizing, and cusp correction. This robust segmentation technique used properties of the image histogram to optimally select a threshold and create closed four-way chain code nuclear segmentations. Each cell nucleus segmentation was treated as an individual object whose properties of segmentation quality were used for criteria to classify each nucleus as: throw away, salvageable, or good. An erosion/dilation procedure and re-thresholding were performed on salvageable nuclei to correct cusps. Results Ten bladder histology images were segmented both by hand and using this automatic segmentation algorithm. The automatic segmentation resulted in a sensitivity of 76.4%, defined as the percentage of hand segmented nuclei that were automatically segmented with good quality. The median proportional difference between hand and automatic segmentations over 42 nuclei each with 95 features used in karyometric analysis was 1.6%. The same procedure was performed on 10 skin histology images with a sensitivity of 83.0% and median proportional difference of 2.6%. Conclusion The close agreement in karyometric features with hand segmentation shows that automated segmentation can be used for analysis of bladder and skin histology images. PMID:19402384

  18. African Dust Aerosols as Atmospheric Ice Nuclei

    NASA Technical Reports Server (NTRS)

    DeMott, Paul J.; Brooks, Sarah D.; Prenni, Anthony J.; Kreidenweis, Sonia M.; Sassen, Kenneth; Poellot, Michael; Rogers, David C.; Baumgardner, Darrel

    2003-01-01

    Measurements of the ice nucleating ability of aerosol particles in air masses over Florida having sources from North Africa support the potential importance of dust aerosols for indirectly affecting cloud properties and climate. The concentrations of ice nuclei within dust layers at particle sizes below 1 pn exceeded 1/cu cm; the highest ever reported with our device at temperatures warmer than homogeneous freezing conditions. These measurements add to previous direct and indirect evidence of the ice nucleation efficiency of desert dust aerosols, but also confirm their contribution to ice nuclei populations at great distances from source regions.

  19. {gamma}-vibrational states in superheavy nuclei

    SciTech Connect

    Sun Yang; Long Guilu; Al-Khudair, Falih; Sheikh, Javid A.

    2008-04-15

    Recent experimental advances have made it possible to study excited structure in superheavy nuclei. The observed states have often been interpreted as quasiparticle excitations. We show that in superheavy nuclei collective vibrations systematically appear as low-energy excitation modes. By using the microscopic Triaxial Projected Shell Model, we make a detailed prediction on {gamma}-vibrational states and their E2 transition probabilities to the ground state band in fermium and nobelium isotopes where active structure research is going on, and in {sup 270}Ds, the heaviest isotope where decay data have been obtained for the ground-state and for an isomeric state.

  20. Computer Model Of Fragmentation Of Atomic Nuclei

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Townsend, Lawrence W.; Tripathi, Ram K.; Norbury, John W.; KHAN FERDOUS; Badavi, Francis F.

    1995-01-01

    High Charge and Energy Semiempirical Nuclear Fragmentation Model (HZEFRG1) computer program developed to be computationally efficient, user-friendly, physics-based program for generating data bases on fragmentation of atomic nuclei. Data bases generated used in calculations pertaining to such radiation-transport applications as shielding against radiation in outer space, radiation dosimetry in outer space, cancer therapy in laboratories with beams of heavy ions, and simulation studies for designing detectors for experiments in nuclear physics. Provides cross sections for production of individual elements and isotopes in breakups of high-energy heavy ions by combined nuclear and Coulomb fields of interacting nuclei. Written in ANSI FORTRAN 77.

  1. Clathrate hydrates in cometary nuclei and porosity

    NASA Technical Reports Server (NTRS)

    Smoluchowski, R.

    1988-01-01

    Possible mechanisms of formation and decomposition of CO2-clathrate hydrate in cometary nuclei are discussed. As far as it is known, this is the only clathrate hydrate which is unstable at low temperatures. Calculation shows that, in accord with other evidence, neither volume nor grain boundary diffusion in the clathrate lattice can be responsible for the rate of these reactions and that a surface mechanism with the attendant sensitivity to pressure must play a crucial role. Density changes accompanying CO2-clathrate decomposition and formation can lead to microporosity and enhanced brittleness or even to fracture of cometary nuclei at low temperatures. Other clathrate hydrates and mixed clathrates are also discussed.

  2. Exotic nuclei with open heavy flavor mesons

    SciTech Connect

    Yasui, Shigehiro; Sudoh, Kazutaka

    2009-08-01

    We propose stable exotic nuclei bound with D and B mesons with respect to heavy quark symmetry. We indicate that an approximate degeneracy of D(B) and D*(B*) mesons plays an important role, and discuss the stability of DN and BN bound states. We find the binding energies 1.4 MeV and 9.4 MeV for each state in the J{sup P}=1/2{sup -} with the I=0 channel. We discuss also possible existence of exotic nuclei DNN and BNN.

  3. Emergent properties of nuclei from ab initio coupled-cluster calculations

    NASA Astrophysics Data System (ADS)

    Hagen, G.; Hjorth-Jensen, M.; Jansen, G. R.; Papenbrock, T.

    2016-06-01

    Emergent properties such as nuclear saturation and deformation, and the effects on shell structure due to the proximity of the scattering continuum and particle decay channels are fascinating phenomena in atomic nuclei. In recent years, ab initio approaches to nuclei have taken the first steps towards tackling the computational challenge of describing these phenomena from Hamiltonians with microscopic degrees of freedom. This endeavor is now possible due to ideas from effective field theories, novel optimization strategies for nuclear interactions, ab initio methods exhibiting a soft scaling with mass number, and ever-increasing computational power. This paper reviews some of the recent accomplishments. We also present new results. The recently optimized chiral interaction NNLO{}{{sat}} is shown to provide an accurate description of both charge radii and binding energies in selected light- and medium-mass nuclei up to 56Ni. We derive an efficient scheme for including continuum effects in coupled-cluster computations of nuclei based on chiral nucleon-nucleon and three-nucleon forces, and present new results for unbound states in the neutron-rich isotopes of oxygen and calcium. The coupling to the continuum impacts the energies of the {J}π =1/{2}-,3/{2}-,7/{2}-,3/{2}+ states in {}{17,23,25}O, and—contrary to naive shell-model expectations—the level ordering of the {J}π =3/{2}+,5/{2}+,9/{2}+ states in {}{53,55,61}Ca. ).

  4. β decay of the exotic Tz=-2 nuclei 48Fe,52Ni , and 56Zn

    NASA Astrophysics Data System (ADS)

    Orrigo, S. E. A.; Rubio, B.; Fujita, Y.; Gelletly, W.; Agramunt, J.; Algora, A.; Ascher, P.; Bilgier, B.; Blank, B.; Cáceres, L.; Cakirli, R. B.; Ganioǧlu, E.; Gerbaux, M.; Giovinazzo, J.; Grévy, S.; Kamalou, O.; Kozer, H. C.; Kucuk, L.; Kurtukian-Nieto, T.; Molina, F.; Popescu, L.; Rogers, A. M.; Susoy, G.; Stodel, C.; Suzuki, T.; Tamii, A.; Thomas, J. C.

    2016-04-01

    The results of a study of the β decays of three proton-rich nuclei with Tz=-2 , namely 48Fe,52Ni , and 56Zn, produced in an experiment carried out at GANIL, are reported. In all three cases we have extracted the half-lives and the total β -delayed proton emission branching ratios. We have measured the individual β -delayed protons and β -delayed γ rays and the branching ratios of the corresponding levels. Decay schemes have been determined for the three nuclei, and new energy levels are identified in the daughter nuclei. Competition between β -delayed protons and γ rays is observed in the de-excitation of the T =2 isobaric analog states in all three cases. Absolute Fermi and Gamow-Teller transition strengths have been determined. The mass excesses of the nuclei under study have been deduced. In addition, we discuss in detail the data analysis taking as a test case 56Zn, where the exotic β -delayed γ -proton decay has been observed.

  5. Inelastic Neutrino Reactions with Light Nuclei and Standing Accretion Shock Instability in Core-Collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Furusawa, S.; Nagakura, H.; Sumiyoshi, K.; Yamada, S.

    2016-01-01

    We perform numerical experiments to investigate the influence of inelastic neutrino reactions with light nuclei on the standing accretion shock instability. The time evolutions of shock waves are calculated with a simple light-bulb approximation for the neutrino transport and a multi-nuclei equation of state. The neutrino absorptions and inelastic interactions with deuterons, tritons, helions and alpha particles are taken into account in the hydrodynamical simulations in addition to the ordinary charged-current interactions with nucleons. Axial symmetry is assumed but no equatorial symmetry is imposed. We show that the heating rates of deuterons reach as high as ∼ 10% of those of nucleons around the bottom of the gain region. On the other hands, alpha particles heat the matter near the shock wave, which is important when the shock wave expands and density and temperature of matter become low. It is also found that the models with heating by light nuclei have different evolutions from those without it in non-linear evolution phase. The matter in the gain region has various densities and temperatures and there appear regions that are locally rich in deuterons and alpha particles. These results indicate that the inelastic reactions of light nuclei, especially deuterons, should be incorporated in the simulations of core-collapse supernovae.

  6. Close to the Sky

    NASA Astrophysics Data System (ADS)

    2007-11-01

    Today, a new ALMA outreach and educational book was publicly presented to city officials of San Pedro de Atacama in Chile, as part of the celebrations of the anniversary of the Andean village. ESO PR Photo 50a/07 ESO PR Photo 50a/07 A Useful Tool for Schools Entitled "Close to the sky: Biological heritage in the ALMA area", and edited in English and Spanish by ESO in Chile, the book collects unique on-site observations of the flora and fauna of the ALMA region performed by experts commissioned to investigate it and to provide key initiatives to protect it. "I thank the ALMA project for providing us a book that will surely be a good support for the education of children and youngsters of San Pedro de Atacama. Thanks to this publication, we expect our rich flora and fauna to be better known. I invite teachers and students to take advantage of this educational resource, which will be available in our schools", commented Ms. Sandra Berna, the Mayor of San Pedro de Atacama, who was given the book by representatives of the ALMA global collaboration project. Copies of the book 'Close to the sky' will be donated to all schools in the area, as a contribution to the education of students and young people in northern Chile. "From the very beginning of the project, ALMA construction has had a firm commitment to environment and local culture, protecting unique flora and fauna species and preserving old estancias belonging to the Likan Antai culture," said Jacques Lassalle, who represented ALMA at the hand-over. "Animals like the llama, the fox or the condor do not only live in the region where ALMA is now being built, but they are also key elements of the ancient Andean constellations. In this sense they are part of the same sky that will be explored by ALMA in the near future." ESO PR Photo 50c/07 ESO PR Photo 50c/07 Presentation of the ALMA book The ALMA Project is a giant, international observatory currently under construction on the high-altitude Chajnantor site in Chile

  7. Decay spectroscopy of neutron-rich rare-earth isotopes and collectivity around double midshell

    SciTech Connect

    Watanabe, Hiroshi

    2015-10-15

    Neutron-rich rare-earth isotopes with A ≈ 170, which locate near the middle of the major shells for both proton and neutron between the doubly magic nuclei {sup 132}Sn and {sup 208}Pb, have been investigated by means of decay spectroscopy techniques at the RIBF facility at RIKEN. The nuclei of interest were produced by in-flight fission of a high-intensity {sup 238}U beam at 345 MeV/u. In this contribution, scientific motivations, the details of experimental procedures, and some prospects of the data analysis are reported.

  8. Gamow-Teller strength distributions for neutron-rich nitrogen, oxygen and fluorine isotopes

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Mei

    2016-08-01

    Gamow-Teller transition properties for neutron-rich nitrogen, oxygen and fluorine isotopes are studied in integrated energy. The structures of these nuclei are described by means of nuclear shell model with the WBT interaction in the p-sd shell space. Calculations of the Gamow-Teller strength distribution reproduce the experimental data reasonably in the low-energy region. For the dripline nucleus 24O, a super Gamow-Teller transition to a single state at excitation energy of 14.72 MeV in 24F is predicted. β-decay half-lives for these nuclei are calculated and compared with the available experimental data.

  9. Photon emission in neutral current interactions with nucleons and nuclei

    SciTech Connect

    Alvarez-Ruso, L.; Nieves, J.; Wang, E.

    2015-05-15

    We report on our study of photon emission induced by E{sub ν} ∼ 1 GeV (anti)neutrino neutral current interactions with nucleons and nuclei. This process is an important background for ν{sub e} appearance oscillation experiments. At the relevant energies, the reaction is dominated by the excitation of the Δ(1232) resonance but there are also non-resonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. We have obtained differential and integrated cross section for the (anti)neutrino-nucleon scattering and compare them with previous results. Furthermore, we have extended the model to nuclear targets taking into account Fermi motion, Pauli blocking and the in-medium modifications of the Δ properties. This study is important in order to reduce systematic effects in neutrino oscillation experiments.

  10. Microscopic cell nuclei segmentation based on adaptive attention window.

    PubMed

    Ko, ByoungChul; Seo, MiSuk; Nam, Jae-Yeal

    2009-06-01

    This paper presents an adaptive attention window (AAW)-based microscopic cell nuclei segmentation method. For semantic AAW detection, a luminance map is used to create an initial attention window, which is then reduced close to the size of the real region of interest (ROI) using a quad-tree. The purpose of the AAW is to facilitate background removal and reduce the ROI segmentation processing time. Region segmentation is performed within the AAW, followed by region clustering and removal to produce segmentation of only ROIs. Experimental results demonstrate that the proposed method can efficiently segment one or more ROIs and produce similar segmentation results to human perception. In future work, the proposed method will be used for supporting a region-based medical image retrieval system that can generate a combined feature vector of segmented ROIs based on extraction and patient data.

  11. X-ray emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R.

    1985-01-01

    It is often held that the X-ray emission from active galactic nuclei (AGN) arises from a region close to the central energy source. Thus X-ray observations may provide the best constraints on the central engine. In particular, the shape of the X-ray continuum gives information about the mechanism for photon generation, X-ray time variability data can constrain the size and mass of the continuum source, and X-ray occultation data give constraints on the relative sizes of the continuum source and the intervening absorbing material (often assumed to be the broad line clouds). In addition, since a fair fraction of the total energy of an AGN is emitted at X-ray wavelengths, direct measurement of the amount and spectral form of this radiation is important for modeling of the optically emitting clouds.

  12. School Closings in Philadelphia

    ERIC Educational Resources Information Center

    Jack, James; Sludden, John

    2013-01-01

    In 2012, the School District of Philadelphia closed six schools. In 2013, it closed 24. The closure of 30 schools has occurred amid a financial crisis, headlined by the district's $1.35 billion deficit. School closures are one piece of the district's plan to cut expenditures and close its budget gap. The closures are also intended to…

  13. Unstable Nuclei in Astrophysics - Proceedings of the International Workshop

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Kajino, T.

    1992-01-01

    The Table of Contents for the full book PDF is as follows: * Preface * Opening Address * I. Explosive Nucleosynthesis in Supernovae and Novae * Explosive Nucleosynthesis in Type II Supernovae * The p-Process in Type II Supernovae * The r-Process in Supernovae * Effects of the 14N(e-, v) 14C(α, γ) 18O Reaction to the Core Mass at the Helium Flash for Low Mass Stars * II. Helium Burning, CNO Cycle and rp-Process * The 12C(α, γ) 16O Cross Section at Low Energies * Helium Burning in Some Astrophysical Scenarios * Measurement of the 1H(13N, γ) 14O Cross Section and Determination of the 14O(1-, T = 1; Eexc = 5.17 MeV) γ-Width * Production of Nuclei on the Proton Drip Line for 31 ≤ Z ≤ 38 * III. Primordial Nucleosynthesis * Signatures of Inhomogeneous Cosmologies; Intermediate-Mass Nucleosynthesis and Radioactive Nuclear Beams * Recent Advances in Primordial Nucleosynthesis * Capture Rates of the 7Li(n, γ)8Li and 12C(n, γ) 13C Reactions by Prompt γ-Ray Detection * Study of the Key Reaction 8Li(α, n) 11B for the Primordial Nucleosynthesis * A QCD Study of Primordial Strange Quark Matter in the Chromoelectric Flux Tube Model (Contributed) * IV. Elemental Abundances, and s- and r-Processes * Shell Structure of Neutron-Rich sd-Shell Nuclei and Its Astrophysical Implication * Half Lives of Long-Lived Tc Isotopes * Evaluation of the CI* and Other Carbonaceous Chondrites as the Solar Abundance Standard * New Generation Calculations of Beta Decay Far from Stability and Astrophysics * Nuclear Masses Far from Stability and Their Relation to r-Process Calculations * Fermion Dynamical Symmetries, Nuclear Masses, and Their Astrophysical Implications * Weak Interaction Rates of sd Shell Nuclei in Stellar Matter (Contributed) * V. New Method in Experimental Nuclear Astrophysics * Experimental Study on the Coulomb Breakup of 14O * Coulomb Dissociation for Nuclear Astrophysics * Some New Developments in Polarized Radioactive Beams * Radioactive Ion Beam Rates from Inverse

  14. Transfer-induced fission of superheavy nuclei

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Zubov, A. S.; Sargsyan, V. V.; Scheid, W.

    2010-07-15

    Possibilities of transfer-induced fission of new isotopes of superheavy nuclei with charge numbers 103-108 are studied for the first time in the reactions {sup 48}Ca+{sup 244,246,248}Cm at energies near the corresponding Coulomb barriers. The predicted cross sections are found to be measurable with the detection of three-body final states.

  15. Quasars: Active nuclei of young galaxies

    NASA Technical Reports Server (NTRS)

    Komberg, B. V.

    1980-01-01

    The hypothetical properties of 'young' galaxies and possible methods of observing them are discussed. It is proposed that star formation first takes place in the central regions of protogalaxies which may appear as quasar-like objects. An evolutionary scheme is outlined in which the radio quasars are transformed in time into the nuclei of radio galaxies.

  16. Form Factors and Radii of Light Nuclei

    SciTech Connect

    Sick, Ingo

    2015-09-15

    We discuss the determination of electromagnetic form factors from the world data on electron–nucleus scattering for nuclei Z ≤ 3, with particular emphasis on the derivation of the moments required for comparison with measurements from electronic/muonic atoms and isotope shifts.

  17. Platelet-Rich Plasma

    PubMed Central

    Cole, Brian J.; Seroyer, Shane T.; Filardo, Giuseppe; Bajaj, Sarvottam; Fortier, Lisa A.

    2010-01-01

    Context: Platelet-rich plasma (PRP) may affect soft tissue healing via growth factors released after platelet degranulation. Because of this potential benefit, clinicians have begun to inject PRP for the treatment of tendon, ligament, muscle, and cartilage injuries and early osteoarthritis. Evidence Acquisition: A PubMed search was performed for studies relating to PRP, growth factors, and soft tissue injuries from 1990 to 2010. Relevant references from these studies were also retrieved. Results: Soft tissue injury is a major source of disability that may often be complicated by prolonged and incomplete recovery. Numerous growth factors may potentiate the healing and regeneration of tendons and ligaments. The potential benefits of biologically enhanced healing processes have led to a recent interest in the use of PRP in orthopaedic sports medicine. There has been widespread anecdotal use of PRP for muscle strains, tendinopathy, and ligament injuries and as a surgical adjuvant to rotator cuff repair, anterior cruciate ligament reconstruction, and meniscal or labral repairs. Although the fascination with this emerging technology has led to a dramatic increase in its use, scientific data supporting this use are still in their infancy. Conclusions: The literature is replete with studies on the basic science of growth factors and their relation to the maintenance, proliferation, and regeneration of various tissues and tissue-derived cells. Despite the promising results of several animal studies, well-controlled human studies are lacking. PMID:23015939

  18. Closed analytical solutions of Bohr Hamiltonian with Manning-Rosen potential model

    NASA Astrophysics Data System (ADS)

    Chabab, M.; Lahbas, A.; Oulne, M.

    2015-11-01

    In the present paper, we have obtained closed analytical expressions for eigenvalues and eigenfunctions of the Bohr Hamiltonian with the Manning-Rosen potential for γ-unstable nuclei as well as exactly separable rotational ones with γ ≈ 0. Some heavy nuclei with known β and γ bandheads have been fitted by using two parameters in the γ-unstable case and three parameters in the axially symmetric prolate deformed one. A good agreement with experimental data has been achieved.

  19. Study of near-stability nuclei populated as fission fragments in heavy-ion fusion reactions

    SciTech Connect

    Fotiadis, Nikolaos; Nelson, Ronald O; Devlin, Matthew; Cizewski, Jolie A; Krucken, Reiner; Clark, R M; Fallon, Paul; Lee, I Yang; Macchiavelli, Agusto O; Becker, John A; Younes, Walid

    2010-01-01

    Examples are presented to illustrate the power of prompt {gamma}-ray spectroscopy of fission fragments from compound nuclei with A {approx} 200 formed in fusion-evaporation reactions in experiments using the Gammasphere Ge-detector array. Complementary methods, such as Coulomb excitation and deep-inelastic processes, are also discussed. In other cases (n, xn{gamma}) reactions on stable isotopes have been used to establish neutron excitation functions for {gamma}-rays using a pulsed 'white'-neutron source, coupled to a high-energy-resolution germanium-detector array. The excitation functions can unambiguously assign {gamma}-rays to a specific reaction product. Results from all these methods bridge the gaps in the systematics of high-spin states between the neutron-deficient and neutron-rich nuclei. Results near shell closures should motivate new shell model calculations.

  20. Structure of N{>=}126 nuclei produced in fragmentation of {sup 238}U

    SciTech Connect

    Al-Dahan, N.; Podolyak, Zs.; Regan, P. H.; Steer, S. J.; Alkhomashi, N.; Gelletly, W.; Walker, P. M.; Farrelly, G.; Deo, A. Y.; Cullen, I. J.; Swan, T.; Bacelar, A. M. Denis; Gorska, M.; Pietri, S. B.; Gerl, J.; Domingo-Pardo, C.; Wollersheim, H. J.; Boutachkov, P.; Farinon, F.; Geissel, H.

    2009-01-28

    The nuclear structure of neutron-rich N{>=}126 nuclei have been investigated following their production via relativistic projectile fragmentation of a E/A = 1 GeV {sup 238}U beam on a Be target. The cocktail of secondary beam products were separated and identified using the GSI FRagment Separator (FRS). The nuclei of interest were implanted in a high-granularity active stopper detector set-up consisting of 6 double sided silicon strip detectors. The associated gamma-ray transitions were detected with the RISING array, consisting of 15 Euroball cluster Ge-detectors. Time-correlated gamma decays from individually identified nuclear species have been recorded, allowing the clean identification of isomeric decays.

  1. Production cross sections from 82Se fragmentation as indications of shell effects close to the neutron drip-line

    NASA Astrophysics Data System (ADS)

    Tarasov, O. B.; Portillo, M.; Morrissey, D. J.; Amthor, A. M.; Baumann, T.; Bazin, D.; Berryman, J. S.; Brown, B. A.; Chubarian, G.; Fukuda, N.; Gade, A.; Ginter, T. N.; Hausmann, M.; Inabe, N.; Kubo, T.; Pereira, J.; Sherrill, B. M.; Stolz, A.; Sumithrarachichi, C.; Thoennessen, M.; Weisshaar, D.

    2013-10-01

    Production cross sections for neutron-rich nuclei from the fragmentation of a 82Se beam at 139 MeV/u with beryllium and tungsten targets have been measured for a large number of nuclei. The nuclides 64Ti,67V,69Cr,72Mn, the most neutron-rich isotopes of the elements 22 <= Z <= 25 , have been observed for the first time. The measured cross sections were used to search for trends in the structure of nuclei around 54Ca and were compared with Abrasion-Ablation calculations under the assumption of various mass models. The results confirm our previous investigations from a similar measurement using a 76Ge beam and can be explained with a modified GXPF1B Hamiltonian where the energy of the f5 / 2 orbit is lowered by 0.5 MeV for neutron-rich isotopes around Z = 20. The subshell gap at N = 34 is reduced compared to the unmodified Hamiltonian.

  2. Ceres' hydrogen-rich regolith

    NASA Astrophysics Data System (ADS)

    Prettyman, Thomas H.; Yamashita, Naoyuki; Castillo-Rogez, Julie C.; Feldman, William C.; Lawrence, David J.; McSween, Harry Y.; Schorghofer, Norbert; Toplis, Michael J.; Forni, Olivier; Joy, Steven P.; Marchi, Simone; Platz, Thomas; Polanskey, Carol A.; De Sanctis, Maria Cristina; Rayman, Marc D.; Raymond, Carol A.; Russell, Christopher T.

    2016-04-01

    Low-altitude mapping of Ceres by Dawn's Gamma Ray and Neutron Detector (GRaND) began in December of 2015. GRaND will continue to acquire data for at least six months in a circular-polar orbit, at an altitude of about 0.8 body radii. Close-proximity enables global mapping of the elemental composition of Ceres' regolith, with regional-scale spatial resolution, similar to that achieved at Vesta. An initial analysis of the data shows that Ceres' regolith is rich in H, consistent with the detection of ammoniated phyllosilicates by Dawn's Visible to InfraRed (VIR) spectrometer. Global maps of neutron and gamma ray counting data reveal a strong latitude variation, with suppressed counts at the poles. Lower bound estimates of the concentration of polar H exceed that found in carbonaceous chondrites, which are the best meteorite analogs for Ceres. Thermal modeling predicts that water ice is stable near the surface at high latitudes, and, given Ceres' low obliquity, water ice and other volatile species may be concentrated in permanently shadowed regions near the poles. Excess hydrogen at high latitudes is likely in the form of water ice within the decimeter depths sensed by GRaND. Changes in the hydration state of phyllosilicates and hydrated salt minerals with temperature could also contribute to observed spatial variations. Some GRaND signatures show evidence for layering of hydrogen, consistent with ice stability models. Differences in the gamma ray spectra of Ceres and Vesta indicate that Ceres' surface is primitive (closely related to carbonaceous chondrite-like compositions), in contrast to Vesta's fractionated igneous composition. Strong gamma rays are observed at 7.6 MeV (Fe), 6.1 MeV (O), and 2.2 MeV (H). With additional accumulation time, it may be possible to quantify or bound the concentration of other elements, such as Mg, Ni, and C. Elements diagnostic of hydrothermal activity (K, Cl, and S) may be detectable if they are present in high concentrations over

  3. RNA-sequencing from single nuclei.

    PubMed

    Grindberg, Rashel V; Yee-Greenbaum, Joyclyn L; McConnell, Michael J; Novotny, Mark; O'Shaughnessy, Andy L; Lambert, Georgina M; Araúzo-Bravo, Marcos J; Lee, Jun; Fishman, Max; Robbins, Gillian E; Lin, Xiaoying; Venepally, Pratap; Badger, Jonathan H; Galbraith, David W; Gage, Fred H; Lasken, Roger S

    2013-12-01

    It has recently been established that synthesis of double-stranded cDNA can be done from a single cell for use in DNA sequencing. Global gene expression can be quantified from the number of reads mapping to each gene, and mutations and mRNA splicing variants determined from the sequence reads. Here we demonstrate that this method of transcriptomic analysis can be done using the extremely low levels of mRNA in a single nucleus, isolated from a mouse neural progenitor cell line and from dissected hippocampal tissue. This method is characterized by excellent coverage and technical reproducibility. On average, more than 16,000 of the 24,057 mouse protein-coding genes were detected from single nuclei, and the amount of gene-expression variation was similar when measured between single nuclei and single cells. Several major advantages of the method exist: first, nuclei, compared with whole cells, have the advantage of being easily isolated from complex tissues and organs, such as those in the CNS. Second, the method can be widely applied to eukaryotic species, including those of different kingdoms. The method also provides insight into regulatory mechanisms specific to the nucleus. Finally, the method enables dissection of regulatory events at the single-cell level; pooling of 10 nuclei or 10 cells obscures some of the variability measured in transcript levels, implying that single nuclei and cells will be extremely useful in revealing the physiological state and interconnectedness of gene regulation in a manner that avoids the masking inherent to conventional transcriptomics using bulk cells or tissues.

  4. Ice Nuclei Production in Volcanic Clouds

    NASA Astrophysics Data System (ADS)

    Few, A. A.

    2012-12-01

    The paper [Durant et al., 2008] includes a review of research on ice nucleation in explosive volcanic clouds in addition to reporting their own research on laboratory measurements focused on single-particle ice nucleation. Their research as well as the research they reviewed were concerned with the freezing of supercooled water drops (250 to 260 K) by volcanic ash particles acting as ice freezing nuclei. Among their conclusions are: Fine volcanic ash particles are very efficient ice freezing nuclei. Volcanic clouds likely contain fine ash concentrations 104 to 105 times greater than found in meteorological clouds. This overabundance of ice nuclei will produce a cloud with many small ice crystals that will not grow larger as they do in meteorological clouds because the cloud water content is widely distributed among the numerous small ice crystals. The small ice crystals have a small fall velocity, thus volcanic clouds are very stable. The small ice crystals are easily lofted into the stratosphere transporting water and adsorbed trace gasses. In this paper we examine the mechanism for the production of the small ice nuclei and develop a simple model for calculating the size of the ice nuclei based upon the distribution of magma around imbedded bubbles. We also have acquired a volcanic bomb that exhibits bubble remnants on its entire surface. The naturally occurring fragments from the volcanic bomb reveal a size distribution consistent with that predicted by the simple model. Durant, A. J., R. A. Shaw, W. I. Rose, Y. Mi, and G. G. J. Ernst (2008), Ice nucleation and overseeding of ice in volcanic clouds, J. Geophys. Res., 113, D09206, doi:10.1029/2007JD009064.

  5. High-Temperature Nucleosynthesis Processes on the Proton-Rich Side of Stability: the Alpha-Rich Freezeout and the rp^2-Process

    NASA Astrophysics Data System (ADS)

    Meyer, Bradley S.

    2001-10-01

    Nucleosynthesis on the proton-rich side of stability has at least two intriguing aspects. First, the most abundant of the stable iron-group isotopes, such as ^48Ti, ^52Cr, and ^56,57Fe, are synthesized as proton-rich, radioactive parents in alpha-rich freezeouts from equilibrium. The production of these radioactive progenitors depends in large measure on reactions on the proton-rich side of stability. The second intriguing aspect is that explosive nucleosynthesis in a hydrogen-rich environment (namely, the rp-process) may be associated with exotic astrophysical settings, such as x-ray bursts, and may be responsible for production of some of the light p-process nuclei (for example, ^92,94Mo and ^96,98Ru). We have developed web-based tools to help nuclear physicists determine which nuclear reactions on the proton-rich side of stability govern the nucleosynthesis in these processes. For the alpha-rich freezeout, one may determine the effect of any one of 2,140 reactions on the yield of any isotope in the nuclear reaction network with the web calculator. As a relevant example, I will discuss the governing role of ^57Ni (n,p)^57Co in the synthesis of the important astronomical observable ^57Co. As for explosive, proton-rich burning, I will discuss the synthesis of p-process nuclei in the repetitive rp-process (the rp^2-process). Movies of the rp^2-process illustrate its important features and give some indications of the important nuclear reactions.

  6. Nuclear Shell Structure and Beta Decay I. Odd A Nuclei II. Even A Nuclei

    DOE R&D Accomplishments Database

    Mayer, M.G.; Moszkowski, S.A.; Nordheim, L.W.

    1951-05-01

    In Part I a systematics is given of all transitions for odd A nuclei for which sufficiently reliable data are available. The allowed or forbidden characters of the transitions are correlated with the positions of the initial and final odd nucleon groups in the nuclear shell scheme. The nuclear shells show definite characteristics with respect to parity of the ground states. The latter is the same as the one obtained from known spins and magnetic moments in a one-particle interpretation. In Part II a systematics of the beta transitions of even-A nuclei is given. An interpretation of the character of the transitions in terms of nuclear shell structure is achieved on the hypothesis that the odd nucleon groups have the same structure as in odd-A nuclei, together with a simple coupling rule between the neutron and proton groups in odd-odd nuclei.

  7. The morphology of cometary nuclei

    NASA Astrophysics Data System (ADS)

    Keller, H. U.; Jorda, L.

    the planetary system (4.5 Gy). Therefore, observed comets could only recently have arrived on their orbits dipping inside the inner Solar System. This reservoir of comets must have been established during the formation process of the planetary system itself. Cometesimals were agglomerated from interstellar/interplanetary gas and dust and scattered out of the inner Solar System by the giant outer planets (Section 2.3). This scheme implies that a central part of a comet, its nucleus, is stable enough to survive these perturbations. It must also be stable enough to pass the vicinity of the sun for many times in the case of a short-period comet. Comets are bright and large when they are close to the sun and fade quickly when they recede beyond about 2AU. Only with the advent of photography and large astronomical telescopes could a comet be followed until it becomes a starlike point source. What makes comets active near the Sun, blowing their appearances up to the order of 105 km? Bright comets often develop tails two orders of magnitude longer. In an attempt to explain the cometary appearance, Bredichin (1903) introduced a mechanical model where repulsive forces drive the particles away from a central condensation. Spectroscopy revealed that dust grains reflect the solar irradiation. In addition, simple molecules, radicals and ions were found as constituents of the cometary coma and tail. The nature of the central condensation remained mysterious for a long time because of the observational dilemma. When the comet is close to the Earth and therefore to the Sun the dense coma obscures the view into its centre. When activity recedes the comet is too far away and too dim for detailed observations of its central condensation. During the middle of the nineteenth century the connection between comets and meteor streams was established. Schiaparelli (1866) calculated the dispersion of cometary dust within the orbital plane. From this time on the perception that the central

  8. How proteins pack into crystals: nuclei achieve translation symmetries by growing.

    PubMed

    Feng, Dan; Zeng, Zong-Hao

    2004-07-01

    How protein molecules pack into a crystal remains problematic. Packing units are direct materials for packing into crystals. The group generator method is introduced for automatically identifying the packing unit. By introducing deviations into the nucleation stage of crystallization, we proved that these deviations diminish in further packing. This process illustrates how translation symmetries are achieved by the growing of nuclei. Two effects, the size effect and the close up effect, are found to behave differently in this process.

  9. New magic nuclei and neutron-proton pairing

    SciTech Connect

    Boboshin, I. N.

    2008-07-15

    Special features of new magic nuclei and their connection with the shell structure are considered. The mechanism of neutron-proton pairing is proposed as a basis for the formation of new magic nuclei. A law of nucleon pairing is introduced. Spin-parity values are explained for a number of odd-odd nuclei.

  10. What Makes a Rich Task?

    ERIC Educational Resources Information Center

    Griffin, Pete

    2009-01-01

    A common view seems to be emerging in the mathematics education world at the moment that the development and use of "rich tasks" is a good thing; a "right thing" to do. There are many examples of these "rich tasks" and teachers are encouraged to use them whenever they can. Professional learners don't just accept this uncritically, but question…

  11. Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of {sup 238}U projectiles at 1A GeV

    SciTech Connect

    Alvarez-Pol, H.; Benlliure, J.; Casarejos, E.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Pereira, J.; Audouin, L.; Enqvist, T.; Schmidt, K.-H.; Yordanov, O.; Junghans, A. R.; Jurado, B.; Rejmund, F.

    2010-10-15

    The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of {sup 238}U projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: {sup 205}Pt, {sup 207-210}Au, {sup 211-216}Hg, {sup 214-217}Tl, {sup 215-220}Pb, {sup 219-224}Bi, {sup 223-227}Po, {sup 225-229}At, {sup 230,231}Rn, and {sup 233}Fr. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

  12. Studies of Nuclei Close to 132Sn Using Single-Neutron Transfer Reactions

    SciTech Connect

    Jones, K. L.; Pain, S. D.; Kozub, R. L.; Adekola, Aderemi S; Bardayan, Daniel W; Blackmon, Jeff C; Catford, Wilton N; Chae, K. Y.; Chipps, K.; Cizewski, J. A.; Erikson, Luke; Gaddis, A. L.; Greife, U.; Grzywacz, R. K.; Harlin, Christopher W; Hatarik, Robert; Howard, Joshua A; James, J.; Kapler, R.; Krolas, W.; Liang, J Felix; Ma, Zhanwen; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D; O'Malley, Patrick; Patterson, N. P.; Paulauskas, Stanley; Shapira, Dan; ShrinerJr., J. F.; Sikora, M.; Sissom, D. J.; Smith, Michael Scott; Swan, T. P.; Thomas, J. S.; Wilson, Gemma L

    2009-01-01

    Neutron transfer reactions were performed in inverse kinematics using radioactive ion beams of 132Sn, 130Sn, and 134Te and deuterated polyethylene targets. Preliminary results are presented. The Q-value spectra for 133Sn, 131Sn and 135Te reveal a number of previously unobserved peaks. The angular distributions are compatible with the expected lf7/2 nature of the ground state of 133Sn, and 2p3/2 for the 3.4 MeV state in 131Sn.

  13. Studies of nuclei close to {sup 132}Sn using single-neutron transfer reactions

    SciTech Connect

    Jones, K. J.; Pain, S. D.; Kozub, R. L.; Howard, J. A.; O'Malley, P. D.; Paulauskas, S. V.; Shriner, J. F.; Sissom, D. J.; Adekola, A. S.; Bardayan, D. W.; Blackmon, J. C.; Liang, J. F.; Nesaraja, C. D.; Shapira, D.; Smith, M. S.; Catford, W. N.; Harlin, C.; Patterson, N. P.; Swan, T. P.; Wilson, G. L.

    2009-03-04

    Neutron transfer reactions were performed in inverse kinematics using radioactive ion beams of {sup 132}Sn, {sup 130}Sn, and {sup 134}Te and deuterated polyethylene targets. Preliminary results are presented. The Q-value spectra for {sup 133}Sn, {sup 131}Sn and {sup 135}Te reveal a number of previously unobserved peaks. The angular distributions are compatible with the expected lf{sub 7/2} nature of the ground state of {sup 133}Sn, and 2p{sub 3/2} for the 3.4 MeV state in {sup 131}Sn.

  14. THE EVOLUTION OF ACTIVE GALACTIC NUCLEI AND THEIR SPINS

    SciTech Connect

    Volonteri, M.; Lasota, J.-P.; Sikora, M.; Merloni, A.

    2013-10-01

    Massive black holes (MBHs), in contrast to stellar mass black holes, are expected to substantially change their properties over their lifetime. MBH masses increase by several orders of magnitude over a Hubble time, as illustrated by Sołtan's argument. MBH spins also must evolve through the series of accretion and mergers events that increase the masses of MBHs. We present a simple model that traces the joint evolution of MBH masses and spins across cosmic time. Our model includes MBH-MBH mergers, merger-driven gas accretion, stochastic fueling of MBHs through molecular cloud capture, and a basic implementation of accretion of recycled gas. This approach aims at improving the modeling of low-redshift MBHs and active galactic nuclei (AGNs), whose properties can be more easily estimated observationally. Despite the simplicity of the model, it does a good job capturing the global evolution of the MBH population from z ∼ 6 to today. Under our assumptions, we find that the typical spin and radiative efficiency of MBHs decrease with cosmic time because of the increased incidence of stochastic processes in gas-rich galaxies and MBH-MBH mergers in gas-poor galaxies. At z = 0, the spin distribution in gas-poor galaxies peaks at spins 0.4-0.8 and is not strongly mass dependent. MBHs in gas-rich galaxies have a more complex evolution, with low-mass MBHs at low redshift having low spins and spins increasing at larger masses and redshifts. We also find that at z > 1 MBH spins are on average the highest in high luminosity AGNs, while at lower redshifts these differences disappear.

  15. Description of superheavy nuclei on the basis of a modified version of the DF3 energy functional

    SciTech Connect

    Tolokonnikov, S. V.; Saperstein, E. E.

    2010-10-15

    The possibility of describing nuclei of the uranium and transuranium region within the generalized method of the energy functional proposed by Fayans and his coauthors is studied. It turned out that, in the functional DF3, it is necessary, for this purpose, to modify the spin-orbit terms whose parameters were chosen in such a way as to describe the binding energies and charge radii of spherical nuclei from calcium to lead. The modified functional (DF3-a) describes well the energy features and charged radii for isotopic chains of uranium and neighboring elements. For deformed nuclei, the deformation was taken into account approximately. The nucleon-drip-line position obtained for these chains proved to be close to the predictions of one of the most successful calculations by the Skyrme-Hartree-Fock method with the HFB-17 functional. It is verified that the use of the functional DF3-a does not impair the description of the properties of lighter nuclei, for which the functional DF3 was devised. Moreover, the modified functional describes better, than the original one, new data on spin-orbit splitting in magic and semimagic nuclei. The calculation with the functional DF3-a confirms the doubly magic nature of the superheavy nuclide {sub 114}{sup 298}X{sub 184}. As for the neutron-separation energies S{sub n} along the isotopic chain of this element, our results are close to the predictions of the so-called micro-macro method.

  16. Study of nuclear structure of odd mass 119-127I nuclei in a phenomenological approach

    NASA Astrophysics Data System (ADS)

    Singh, Dhanvir; Gupta, Anuradha; Kumar, Amit; Sharma, Chetan; Singh, Suram; Bharti, Arun; Khosa, S. K.; Bhat, G. H.; Sheikh, J. A.

    2016-08-01

    By using the phenomenological approach of Projected Shell Model (PSM), the positive and negative-parity band structures of odd mass neutron-rich 119-127I nuclei have been studied with the deformed single-particle states generated by the standard Nilsson potential. For these isotopes, the band structures have been analyzed in terms of quasi-particles configurations. The phenomenon of backbending in moment of inertia is also studied in the present work. Besides this, the reduced transition probabilities, i.e. B (E 2) and B (M 1), are obtained from the PSM wavefunction for the first time for yrast bands of these isotopes.

  17. Ice Nuclei in Mid-Latitude Cirrus: Preliminary Results from a New Counterflow Virtual Impactor (CVI) Aircraft Inlet

    NASA Astrophysics Data System (ADS)

    Froyd, K. D.; Cziczo, D. J.; Murphy, D. M.; Kulkarni, G.; Lawson, P.

    2011-12-01

    Cirrus cloud properties are strongly governed by the mechanism of ice particle formation and by the number and effectiveness of ambient ice nuclei. Airborne measurements of ice nuclei reveal new nucleation mechanisms, provide constraints on microphysical models, and guide laboratory investigations. For over two decades the Counterflow Virtual Impactor (CVI) inlet has remained the prevailing approach for sampling cloud particles to measure ice nuclei from an aircraft platform. However, traditional CVI inlets have fundamental limitations when operating on high speed aircraft, where only a small fraction of ambient cloud particles are typically sampled. A novel 'folded' CVI was constructed and deployed during the NASA MACPEX 2011 campaign. The flow design of this inlet effectively doubles the CVI length and thereby increases the size range of captured cirrus particles. Additional design elements such as an internal vortex flow, a neon carrier gas, and an infrared laser further improve the capture and evaporation of ice crystals. Preliminary results of ice nuclei composition measured by the PALMS single-particle mass spectrometer are presented from the MACPEX campaign. Examples of ice nuclei from mid-latitude cirrus are shown, including mineral dust, organic-rich aerosol with amine and diacid components, and lead-containing aerosol.

  18. THE INFLUENCE OF INELASTIC NEUTRINO REACTIONS WITH LIGHT NUCLEI ON THE STANDING ACCRETION SHOCK INSTABILITY IN CORE-COLLAPSE SUPERNOVAE

    SciTech Connect

    Furusawa, Shun; Nagakura, Hiroki; Yamada, Shoichi; Sumiyoshi, Kohsuke

    2013-09-01

    We perform numerical experiments to investigate the influence of inelastic neutrino reactions with light nuclei on the standing accretion shock instability (SASI). The time evolution of shock waves is calculated with a simple light-bulb approximation for the neutrino transport and a multi-nuclei equation of state. The neutrino absorptions and inelastic interactions with deuterons, tritons, helions, and alpha particles are taken into account in the hydrodynamical simulations. In addition, the effects of ordinary charged-current interactions with nucleons is addressed in the simulations. Axial symmetry is assumed but no equatorial symmetry is imposed. We show that the heating rates of deuterons reach as high as {approx}10% of those of nucleons around the bottom of the gain region. On the other hand, alpha particles are heated near the shock wave, which is important when the shock wave expands and the density and temperature of matter become low. It is also found that the models with heating by light nuclei evolve differently in the non-linear phase of SASI than do models that lack heating by light nuclei. This result is because matter in the gain region has a varying density and temperature and therefore sub-regions appear that are locally rich in deuterons and alpha particles. Although the light nuclei are never dominant heating sources and they work favorably for shock revival in some cases and unfavorably in other cases, they are non-negligible and warrant further investigation.

  19. Monopole strength function of deformed superfluid nuclei

    NASA Astrophysics Data System (ADS)

    Stoitsov, M.; Kortelainen, M.; Nakatsukasa, T.; Losa, C.; Nazarewicz, W.

    2011-10-01

    We present an efficient method for calculating strength functions using the finite-amplitude method (FAM) for deformed superfluid heavy nuclei within the framework of the nuclear density functional theory. We demonstrate that FAM reproduces strength functions obtained with the fully self-consistent quasiparticle random-phase approximation (QRPA) at a fraction of the computational cost. As a demonstration, we compute the isoscalar and isovector monopole strengths for strongly deformed configurations in 100Zr and 240Pu by considering huge quasiparticle QRPA spaces. Our approach to FAM, based on Broyden's iterative procedure, opens the possibility for large-scale calculations of strength distributions in well-deformed superfluid nuclei across the nuclear landscape.

  20. Antiproton Production by CR on Air Nuclei

    NASA Technical Reports Server (NTRS)

    Maskalenko, I. V.; Mashnik, S. G.

    2003-01-01

    Recent measurements of the cosmic ray (CR) antiproton flux have been shown to challenge existing CR propagation models. In particular, the conventional reacceleration model designed to match secondary/primary nuclei ratios produces too few antiprotons. Recently there appear some indications that the atmospheric contribution to antiproton production is considerably underestimated, which implies that antiproton CR flux might be lower. This may be the primary reason of the discrepancy discovered in CR propagation. We use the Los Alamos version of the Quark-Gluon String Model code LAQGSM together with available data on antiproton production on nuclei to analyse the accuracy of existing parameterizations of antiproton production cross section. The LAQGSM model has been shown to reproduce well nuclear reactions and hadronic data in the range 0.01-800 GeV/nucleon.

  1. Nuclei at HERA and heavy ion physics

    SciTech Connect

    Gavin, S.; Strikman, M.

    1995-12-31

    Copies of 16 viewgraph sets from a workshop held at Brookhaven National Laboratory, 17-18 November, 1995. Titles of talks: HERA: The Present; HERA: Potential with Nuclei; Review of Hadron-Lepton Nucleus Data; Fermilab E665: results in muon scattering; Interactions of Quarks and Gluons with Nuclear Matter; Rescattering in Nuclear Targets for Photoproduction and DIS; Structure Functions and Nuclear Effect at PHENIX; Probing Spin-Averaged and Spin-Dependent Parton Distributions Using the Solenoidal Tracker at RHIC (STAR); Jet Quenching in eA, pA, AA; Nuclear Gluon Shadowing via Continuum Lepton Pairs; What can we learn from HERA with a colliding heavy ion beam? The limiting curve of leading particles at infinite A; Coherent Production of Vector Mesons off Light Nuclei in DIS; A Model of High Parton Densities in PQCD; Gluon Production for Weizaecker-Williams Field in Nucleus-Nucleus Collisions; Summary Talk.

  2. Effective field theory for lattice nuclei.

    PubMed

    Barnea, N; Contessi, L; Gazit, D; Pederiva, F; van Kolck, U

    2015-02-01

    We show how nuclear effective field theory (EFT) and ab initio nuclear-structure methods can turn input from lattice quantum chromodynamics (LQCD) into predictions for the properties of nuclei. We argue that pionless EFT is the appropriate theory to describe the light nuclei obtained in LQCD simulations carried out at pion masses heavier than the physical pion mass. We solve the EFT using the effective-interaction hyperspherical harmonics and auxiliary-field diffusion Monte Carlo methods. Fitting the three leading-order EFT parameters to the deuteron, dineutron, and triton LQCD energies at m_{π}≈800  MeV, we reproduce the corresponding alpha-particle binding and predict the binding energies of mass-5 and mass-6 ground states. PMID:25699436

  3. Onset of rotational damping in superdeformed nuclei

    NASA Astrophysics Data System (ADS)

    Yoshida, K.; Matsuo, M.

    1997-02-01

    We discuss damping of the collective rotational motion in A ˜ 150 superdeformed nuclei by means of a shell-model combining the cranked Nilsson mean field and the surface and volume delta two-body residual forces. It is shown that, because of the shell structure associated with the superdeformed mean field, onset energy of the rotational damping becomes Ex ˜ 1.5-3 MeV above the yrast line, with significant variation for different neutron and proton numbers. The mechanism of the shell structure effect is investigated through detailed analysis of level densities in superdeformed nuclei. The variation in onset of damping is associated with variation in the single-particle structure at the Fermi surface.

  4. Shell model for warm rotating nuclei

    SciTech Connect

    Matsuo, M.; Yoshida, K.; Dossing, T.

    1996-12-31

    Utilizing a shell model which combines the cranked Nilsson mean-field and the residual surface and volume delta two-body forces, the authors discuss the onset of rotational damping in normal- and super-deformed nuclei. Calculation for a typical normal deformed nucleus {sup 168}Yb indicates that the rotational damping sets in at around 0.8 MeV above the yrast line, and about 30 rotational bands of various length exists at a given rotational frequency, in overall agreement with experimental findings. It is predicted that the onset of rotational damping changes significantly in different superdeformed nuclei due to the variety of the shell gaps and single-particle orbits associated with the superdeformed mean-field.

  5. Collective properties of drip-line nuclei

    SciTech Connect

    Hamamoto, I.; Sagawa, H.

    1996-12-31

    Performing the spherical Hartree-Fock (HF) calculations with Skyrme interactions and, then, using RPA solved in the coordinate space with the Green`s function method, the authors have studied the effect of the unique shell structure as well as the very low particle threshold on collective modes in drip line nuclei. In this method a proper strength function in the continuum is obtained, though the spreading width of collective modes is not included. They have examined also one-particle resonant states in the obtained HF potential. Unperturbed particle-hole (p-h) response functions are carefully studied, which contain all basic information on the exotic behaviour of the RPA strength function in drip line nuclei.

  6. Monopole Strength Function of Deformed Superfluid Nuclei

    SciTech Connect

    Stoitsov, M. V.; Kortelainen, E. M.; Nakatsukasa, T.; Losa, C.; Nazarewicz, Witold

    2011-01-01

    We present an efficient method for calculating strength functions using the finite amplitude method (FAM) for deformed superfluid heavy nuclei within the framework of the nuclear density functional theory. We demonstrate that FAM reproduces strength functions obtained with the fully self-consistent quasi-particle random-phase approximation (QRPA) at a fraction of computational cost. As a demonstration, we compute the isoscalar and isovector monopole strength for strongly deformed configurations in ^{240}Pu by considering huge quasi-particle QRPA spaces. Our approach to FAM, based on Broyden's iterative procedure, opens the possibility for large-scale calculations of strength distributions in well-bound and weakly bound nuclei across the nuclear landscape.

  7. [Bilateral infarction of the caudate nuclei].

    PubMed

    Mrabet, A; Mrad-Ben Hammouda, I; Abroug, Z; Smiri, W; Haddad, A

    1994-01-01

    We report the case of a 57-year-old right-handed woman, with a history of hypertension, who, in February 1990, suddenly developed behavioral and cognitive abnormalities. Prior to the onset of her illness she had been normal. On examination, neuropsychological testing (Wechsler Mental Test, Wechsler Adult Intelligence Scale Revised, Knox Cube Test) elicited attention abnormalities, decreased recent memory, apathy, reduced spontaneity and initiative and left hemiparesia. CT scan showed small low density areas in the head of both caudate nuclei and right internal capsule, indicating infarction. Two years later, the deficit had partially resolved. Apathy persisted; psychometry showed an IQ of 57. Bilateral damage to the head of the caudate nuclei disrupt cortical-subcortical connections. The caudate nucleus is an essential component of basal ganglia-thalamo-cortical circuitry and its contribution to cognitive functions and behavior appears to be important. PMID:7801044

  8. Surviving a School Closing

    ERIC Educational Resources Information Center

    De Witt, Peter M.; Moccia, Josephine

    2011-01-01

    When a beloved school closes, community emotions run high. De Witt and Moccia, administrators in the Averill Park School District in upstate New York, describe how their district navigated through parents' anger and practical matters in closing a small neighborhood elementary school and transferring all its students to another school. With a group…

  9. Electromagnetic interactions with nuclei and nucleons

    SciTech Connect

    Thornton, S.T.; Sealock, R.M.

    1990-11-10

    This report discusses the following topics: general LEGS work; photodisintegration of the deuteron; progress towards other experiments; LEGS instrumentation; major LEGS software projects; NaI detector system; nucleon detector system; waveshifting fibers; EGN prototype detector for CEBAF; photon beam facility at CEBAF; delta electroproduction in nuclei; quasielastic scattering and excitation of the Delta by {sup 4}He(e,e{prime}); and quasielastic scattering at high Q{sup 2}.

  10. Accretion disk thermal instability in galactic nuclei

    NASA Astrophysics Data System (ADS)

    Mineshige, S.; Shields, G. A.

    1990-03-01

    The nonlinear evolution and spatial propagation of the thermal instability in accretion disks in galactic nuclei are investigated. Integrations of the vertical structure of the disks are described for different alpha prescriptions, and the thermal stability is examined. Global time-dependent calculations of the unstable disks are performed which show that there are two distinct types of behavior according to the assumed prescription for the viscosity parameter: the 'purr' type and the 'roar' type. The roar type is analyzed in some detail.

  11. How do nuclei really vibrate or rotate

    SciTech Connect

    Andresen, H.G.; Kunz, J.; Mosel, U.; Mueller, M.; Schuh, A.; Wust, U.

    1983-01-01

    By means of the adiabatic cranking model the properties of the current and velocity fields of nuclear quadrupole vibrations for even-even nuclei in the rare-earth region are investigated. BCS correlated wave functions based on the Nilsson single particle Hamiltonian have been used. The current fields are analyzed in terms of vector spherical harmonics. The realistic microscopic currents show a vortex structure not present in the classical irrotational flow. The microscopic origin of the vortex structure is investigated.

  12. Green's function calculations of light nuclei

    NASA Astrophysics Data System (ADS)

    Sun, ZhongHao; Wu, Qiang; Xu, FuRong

    2016-09-01

    The influence of short-range correlations in nuclei was investigated with realistic nuclear force. The nucleon-nucleon interaction was renormalized with V lowk technique and applied to the Green's function calculations. The Dyson equation was reformulated with algebraic diagrammatic constructions. We also analyzed the binding energy of 4He, calculated with chiral potential and CD-Bonn potential. The properties of Green's function with realistic nuclear forces are also discussed.

  13. Superconducting magnetic spectrometer for cosmic ray nuclei.

    NASA Technical Reports Server (NTRS)

    Smith, L. H.; Buffington, A.; Wahlig, M. A.; Dauber, P.

    1972-01-01

    This paper describes the design, calibration, and operation of a magnetic spectrometer for particle astronomy. The spectrometer consists of a superconducting magnet, optical spark chambers, scintillation detectors, and associated electronics. The instrument has been flown in a balloon gondola to 4.8 g/sq cm residual atmosphere, where it was used to analyze the charge and differential rigidity spectra of primary nuclei from 5 to 100 GeV/c.

  14. Understanding active galactic nuclei: peeling the onion.

    NASA Astrophysics Data System (ADS)

    Krolik, J. H.

    A brief review is presented of selected current problems in understanding active galactic nuclei, with special emphasis on the contributions that X-ray observations can make. Questions having to do with: how the character of the host galaxy influences nuclear activity; emission line regions; the border between the nucleus and the stellar portion of the active galaxy; radiation of the nonthermal continuum; and the possible existence of an accretion disk are touched upon.

  15. Gamma rays from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    1990-01-01

    The general properties of Active Galactic Nuclei (AGN) and quasars are reviewed with emphasis on their continuum spectral emission. Two general classes of models for the continuum are outlined and critically reviewed in view of the impending GRO (Gamma Ray Observatory) launch and observations. The importance of GRO in distinguishing between these models and in general in furthering the understanding of AGN is discussed. The very broad terms the status of the current understanding of AGN are discussed.

  16. Velocity distributions for fast rotating nuclei

    SciTech Connect

    Wu, X.; Zhang, X.; Zhuo, Y.; Feng, R.

    1982-01-01

    The velocity field is calculated on the basis of the exact wave functions of the cranked deformed harmonic oscillator by including the term of ..delta..N = 2 subject to the conditions of isotropic velocity distribution and self-consistency between potential and density distribution. We study the characteristics of velocity distributions of nuclei with the large rotational frequencies. We also discuss the effects of two types of self-consistency conditions on the velocity distributions.

  17. Deeply virtual Compton scattering off nuclei

    SciTech Connect

    Voutier, Eric

    2009-01-01

    Deeply virtual Compton scattering (DVCS) is the golden exclusive channel for the study of the partonic structure of hadrons, within the universal framework of generalized parton distributions (GPDs). This paper presents the aim and general ideas of the DVCS experimental program off nuclei at the Jefferson Laboratory. The benefits of the study of the coherent and incoherent channels to the understanding of the EMC (European Muon Collaboration) effect are discussed, along with the case of nuclear targets to access neutron GPDs.

  18. Complex fragment emission from hot compound nuclei

    SciTech Connect

    Moretto, L.G.

    1986-03-01

    The experimental evidence for compound nucleus emission of complex fragments at low energies is used to interpret the emission of the same fragments at higher energies. The resulting experimental picture is that of highly excited compound nuclei formed in incomplete fusion processes which decay statistically. In particular, complex fragments appear to be produced mostly through compound nucleus decay. In the appendix a geometric-kinematic theory for incomplete fusion and the associated momentum transfer is outlined. 10 refs., 19 figs.

  19. The fractionation of nuclei from mammalian cells by zonal centrifugation

    PubMed Central

    Johnston, I. R.; Mathias, A. P.; Pennington, F.; Ridge, D.

    1968-01-01

    1. Purified liver nuclei from adult rats separate into two main zones when centrifuged in the slow-speed zonal rotor. One zone contains diploid nuclei, the other tetraploid. 2. The effect of age on the pattern of rat liver ploidy was examined. Tetraploid nuclei are virtually absent from young animals. They increase in proportion steadily with age. Partial hepatectomy disturbs the pattern of ploidy. 3. The zonal centrifuge permits the separation of diploid, tetraploid, octaploid and hexadecaploid nuclei from mouse liver. 4. Rat liver nuclei are isopycnic with sucrose solutions of density 1·35 at 5°. ImagesFig. 1.PLATE 1Fig. 9. PMID:4876099

  20. How to assess species richness along single environmental gradients? Implications of potential versus realized species distributions.

    PubMed

    van Goethem, Thomas M W J; Huijbregts, Mark A J; Wamelink, G W Wieger; Schipper, Aafke M

    2015-05-01

    Quantifying relationships between species richness and single environmental factors is challenging as species richness typically depends on multiple environmental factors. Recently, various methods have been proposed to tackle this challenge. Using a dataset comprising field observations of grassland vegetation and measured pH values, we compared three methods for deriving species richness response curves. One of the methods estimates species richness close to the maximum species richness observed at the sites, whereas the other two provide estimates of the potential species richness along the environmental gradient. Our response curves suggest that potential species richness of grasslands is slightly more sensitive to acidification than realized plant species richness. However, differences in corresponding environmental quality standards (EQS) for acidification were small compared to intrinsic spatial differences in natural soil pH, indicating that natural background values are more important to consider in the derivation of EQS for pH than methodological differences between the three approaches. PMID:25705854

  1. How to assess species richness along single environmental gradients? Implications of potential versus realized species distributions.

    PubMed

    van Goethem, Thomas M W J; Huijbregts, Mark A J; Wamelink, G W Wieger; Schipper, Aafke M

    2015-05-01

    Quantifying relationships between species richness and single environmental factors is challenging as species richness typically depends on multiple environmental factors. Recently, various methods have been proposed to tackle this challenge. Using a dataset comprising field observations of grassland vegetation and measured pH values, we compared three methods for deriving species richness response curves. One of the methods estimates species richness close to the maximum species richness observed at the sites, whereas the other two provide estimates of the potential species richness along the environmental gradient. Our response curves suggest that potential species richness of grasslands is slightly more sensitive to acidification than realized plant species richness. However, differences in corresponding environmental quality standards (EQS) for acidification were small compared to intrinsic spatial differences in natural soil pH, indicating that natural background values are more important to consider in the derivation of EQS for pH than methodological differences between the three approaches.

  2. Oxygen Compatibility Screening Tests in Oxygen-Rich Combustion Environment

    NASA Technical Reports Server (NTRS)

    Eckel, Anerew J.

    1997-01-01

    The identification and characterization of oxygen-rich compatible materials enables full-flow, staged combustion designs. Although these oxygen-rich designs offer significant cost, performance, and reliability benefits over existing systems, they have never been used operationally by the United States. If these systems are to be realized, it is critical to understand the long-term oxidative stability in high-temperature, high-pressure, oxygen-rich combustion environments. A unique facility has been constructed at the NASA Lewis Research Center to conduct tests of small-scale rocket engine materials and subcomponents in an oxygen-rich combustion environment that closely approximates a full-scale rocket engine. Thus, a broad range of advanced materials and concepts can be screened in a timely manner and at a relatively low cost.

  3. New fission valley for /sup 258/Fm and nuclei beyond

    SciTech Connect

    Moeller, P.; Nix, J.R.; Swiatecki, W.J.

    1986-01-01

    Experimental results on the fission properties of nuclei close to /sup 264/Fm show sudden and large changes with a change of only one or two neutrons or protons. The nucleus /sup 258/Fm, for instance, undergoes symmetric fission with a half-life of about 0.4 ms and a kinetic energy peaked at about 235 MeV whereas /sup 256/Fm undergoes asymmetric fission with a half-life of about 3 h and a kinetic energy peaked at about 200 MeV. Qualitatively, these sudden changes hve been postulated to be due to the emergence of fragment shells in symmetric fission products close to /sup 132/Sn. A quantitative calculation that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. The implications of the new fission valley on the stability of the heaviest elements is discussed. 33 refs., 12 figs.

  4. Chromatin associations in Arabidopsis interphase nuclei

    PubMed Central

    Schubert, Veit; Rudnik, Radoslaw; Schubert, Ingo

    2014-01-01

    The arrangement of chromatin within interphase nuclei seems to be caused by topological constraints and related to gene expression depending on tissue and developmental stage. In yeast and animals it was found that homologous and heterologous chromatin association are required to realize faithful expression and DNA repair. To test whether such associations are present in plants we analyzed Arabidopsis thaliana interphase nuclei by FISH using probes from different chromosomes. We found that chromatin fiber movement and variable associations, although in general relatively seldom, may occur between euchromatin segments along chromosomes, sometimes even over large distances. The combination of euchromatin segments bearing high or low co-expressing genes did not reveal different association frequencies probably due to adjacent genes of deviating expression patterns. Based on previous data and on FISH analyses presented here, we conclude that the global interphase chromatin organization in A. thaliana is relatively stable, due to the location of its 10 centromeres at the nuclear periphery and of the telomeres mainly at the centrally localized nucleolus. Nevertheless, chromatin movement enables a flexible spatial genome arrangement in plant nuclei. PMID:25431580

  5. Few-Body Models of Light Nuclei

    NASA Astrophysics Data System (ADS)

    Ershov, S. N.; Vaagen, J. S.; Zhukov, M. V.

    2015-06-01

    Experiments confirm a variety of cluster structures in many light nuclei. The observation of nuclear halos at drip-lines has accentuated the question of the degrees of freedom for bound and low-lying continuum states. In these cases the many-body dynamics of nuclear structure may be well approximated by few-body cluster models that often suggest conceptually simple approaches explaining successfully many features of light nuclei. Thus few-body cluster models have been successfully used for description of the nuclear structure of weakly bound halo nuclei and their emergent cluster degrees of freedom. They have attractive features supplying in a most transparent way the asymptotic behavior and continuum properties of weakly bound systems. Such models assume a separation in internal cluster (core) degrees of freedom and the relative motion of few-body constituents. Such separation is only an approximation, and low-lying states appear where the core cannot be considered as inert system and additional degrees of freedom connected to excited core states have to be taken into account. For fixed total angular momentum a coupling to excited core states having different spins involves additional partial waves into the consideration. This allows to account for some emergent (collective) core degrees of freedom and gives a more realistic description of nuclear properties. It is an analogue to increasing the number of shells within the framework of shell-model approaches. Some examples from recent nuclear structure exploration within few-body halo cluster models are presented.

  6. Potential energy surfaces of superheavy nuclei

    SciTech Connect

    Bender, M.; Rutz, K.; Maruhn, J.A.; Greiner, W.; Reinhard, P.-G. Rutz, K.; Maruhn, J.A.; Greiner, W.

    1998-10-01

    We investigate the structure of the potential energy surfaces of the superheavy nuclei {sub 158}{sup 258}Fm{sub 100}, {sub 156}{sup 264}Hs{sub 108}, {sub 166}{sup 278}112, {sub 184}{sup 298}114, and {sub 172}{sup 292}120 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. {copyright} {ital 1998} {ital The American Physical Society}

  7. Qβ Measurements of Neutron-Rich Isotopes in the Mass Region 147≤A≤152

    NASA Astrophysics Data System (ADS)

    Ikuta, Tomohiko; Taniguchi, Akihiro; Yamamoto, Hiroshi; Kawade, Kiyoshi; Kawase, Yoichi

    1995-09-01

    The systematic Qβ measurements of 14 neutron-rich nuclei in the mass region from A=147 to A=152 have been performed with an HPGe detector. Neutron rich nuclei were mass separated from the thermal neutron induced fission of 235U using a He-jet type on-line isotope separator which has been developed at the Kyoto University Reactor (KUR). From β-ray singles and β-γ coincidence measurements, the Qβ values of 147La, 147-150Ce, 147-152Pr, 152Nd and 152Pm have been determined. The Qβ values of 152Pr and 152Nd have been measured for the first time. The atomic masses derived from the Qβ values are compared with the predictions of theoretical mass calculations.

  8. Shell effects in hot nuclei and their influence on nuclear composition in supernova matter

    NASA Astrophysics Data System (ADS)

    Nishimura, Suguru; Takano, Masatoshi

    2014-05-01

    We calculate nuclear composition in supernova (SN) matter explicitly taking into account the temperature dependence of nuclear shell effects. The abundance of nuclei in SN matter is important in the dynamics of core-collapse supernovae and, in recently constructed equations of state (EOS) for SN matter, the composition of nuclei are calculated assuming nuclear statistical equilibrium wherein the nuclear internal free energies govern the composition. However, in these EOS, thermal effects on the shell energy are not explicitly taken into account. To address this shortfall, we calculate herein the shell energies of hot nuclei and examine their influence on the composition of SN matter. Following a simplified macroscopic-microscopic approach, we first calculate single-particle (SP) energies by using a spherical Woods-Saxon potential. Then we extract shell energies at finite temperatures using Strutinsky method with the Fermi distribution as the average occupation probability of the SP levels. The results show that at relatively low temperatures, shell effects are still important and magic nuclei are abundant. However, at temperatures above approximately 2 MeV, shell effects are almost negligible, and the mass fractions with shell energies including the thermal effect are close to those obtained from a simple liquid drop model at finite temperatures.

  9. Toward a general theory of conical intersections in systems of identical nuclei

    NASA Astrophysics Data System (ADS)

    Keating, Sean P.; Mead, C. Alden

    1987-02-01

    It has been shown previously that the Herzberg-Longuet-Higgins sign change produced in Born-Oppenheimer electronic wave functions when the nuclei traverse a closed path around a conical intersection has implications for the symmetry of wave functions under permutations of identical nuclei. For systems of three or four identical nuclei, there are special features present which have facilitated the detailed analysis. The present paper reports progress toward a general theory for systems of n nuclei. For n=3 or 4, the two key functions which locate conical intersections and define compensating phase factors can conveniently be defined so as to transform under permutations according to a two-dimensional irreducible representation of the permutation group. Since such representations do not exist for n>4, we have chosen to develop a formalism in terms of lab-fixed electronic basis functions, and we show how to define the two key functions in principle. The functions so defined both turn out to be totally symmetric under permutations. We show how they can be used to define compensating phase factors so that all modified electronic wave functions are either totally symmetric or totally antisymmetric under permutations. A detailed analysis is made to cyclic permutations in the neighborhood of Dnh symmetry, which can be extended by continuity arguments to more general configurations, and criteria are obtained for sign changes. There is a qualitative discussion of the treatment of more general permutations.

  10. Shell effects in hot nuclei and their influence on nuclear composition in supernova matter

    SciTech Connect

    Nishimura, Suguru; Takano, Masatoshi

    2014-05-02

    We calculate nuclear composition in supernova (SN) matter explicitly taking into account the temperature dependence of nuclear shell effects. The abundance of nuclei in SN matter is important in the dynamics of core-collapse supernovae and, in recently constructed equations of state (EOS) for SN matter, the composition of nuclei are calculated assuming nuclear statistical equilibrium wherein the nuclear internal free energies govern the composition. However, in these EOS, thermal effects on the shell energy are not explicitly taken into account. To address this shortfall, we calculate herein the shell energies of hot nuclei and examine their influence on the composition of SN matter. Following a simplified macroscopic-microscopic approach, we first calculate single-particle (SP) energies by using a spherical Woods-Saxon potential. Then we extract shell energies at finite temperatures using Strutinsky method with the Fermi distribution as the average occupation probability of the SP levels. The results show that at relatively low temperatures, shell effects are still important and magic nuclei are abundant. However, at temperatures above approximately 2 MeV, shell effects are almost negligible, and the mass fractions with shell energies including the thermal effect are close to those obtained from a simple liquid drop model at finite temperatures.

  11. Atmospheric Entry Heating: Evidence for Texturally Heterogeneous Comet Nuclei?

    NASA Astrophysics Data System (ADS)

    Rietmeijer, F. J. M.

    1993-07-01

    Chondritic porous (CP) and chondritic smooth (CS) interplanetary dust particle (IDP) texture and petrology alone cannot distinguish asteroidal from cometary debris and give no evidence that the IDPs are debris of different protoplanets, e.g., active, dormant, and extinct comet nuclei and carbon-rich asteroids [1]. There is probably a gradual transition from active to extinct comet nuclei with asteroidlike behaviour, and cometary orbits might evolve into asteroidlike orbits [2], which will hamper efforts to match IDPs to a particular protoplanet type. Recently, chondritic IDP morphology, mineralogy, and He release temperatures are used to link individual IDPs to asteroids or comets. Yet the observation that CP IDPs occur with both cometary and asteroidal orbits [3] suggests we should explore the notion that chondritic IDP protoplanets are texturally heterogeneous bodies containing both CS IDP and CP IDP-like domains. Particle L2005B22, 7.5 mm x 5.1 mm in size, has a CI bulk composition in FeO- MgO-SiO2 space. Its highly vesicular texture indicates stage C of the type S sphere ablation sequence [4] and supports degassing of a volatile-rich precursor. A relic forsterite crystal, Mg/(Mg + Fe^2+) = 0.93-1.0 is the only large (1.8 mm x 0.8 mm) grain in a poorly crystalline matrix. The olivine interior contains a minor laihunite component. The grain has a ~45-nm-wide vesicular rim where it abuts the particle outer surface. The matrix contains densely packed round crystals up to 10 nm in size and larger, up to 12 nm x 37 nm, euhedral olivine, orthopyroxene, and iron oxide crystals. Vesicles in the frotty matrix increase in size toward the particle exterior and along vugs. The matrix shows local flow textures. Single maghemite nanocrystals and partial maghemite rims (<180 nm wide) occur along the exterior. Thin (~30 nm) crescents decorate the vugs. This maghemite is evidence that the IDP was heated during atmospheric entry. The vesicular rim on olivine suggests evaporation

  12. Astrophysical quests for neutron capture data of unstable nuclei

    NASA Astrophysics Data System (ADS)

    Käppeler, F.

    2016-11-01

    The abundances of the chemical elements heavier than iron can be attributed in about equal parts to the r and to the s process, which are taking place in supernova explosions and during the He and C burning phases of stellar evolution, respectively. So far, quantitative studies on the extremely short-lived neutron-rich nuclei constituting the ( n, γ) network of the r process are out of reach. On the contrary, the situation for the s -process is far advanced, as the reaction path of the s process from 12C to the Pb/Bi region is located within the valley of stability. Accordingly, a comprehensive database of experimental ( n, γ) cross sections has been established. While for many stable isotopes the necessary accuracy is still to be reached, reliable cross sections for the involved unstable isotopes are almost completely missing. Because of the intrinsic γ background of radioactive samples, successful time-of-flight measurements are depending on intense pulsed neutron sources. Such data are fundamental for our understanding of branchings in the s -process reaction path, which carry important model-independent information on neutron flux and temperature in the deep stellar interior.

  13. Relativistic effective interaction for nuclei, giant resonances, and neutron stars

    SciTech Connect

    Fattoyev, F. J.; Piekarewicz, J.; Horowitz, C. J.; Shen, G.

    2010-11-15

    Nuclear effective interactions are useful tools in astrophysical applications especially if one can guide the extrapolations to the extremes regions of isospin and density that are required to simulate dense, neutron-rich systems. Isospin extrapolations may be constrained in the laboratory by measuring the neutron skin thickness of a heavy nucleus, such as {sup 208}Pb. Similarly, future observations of massive neutron stars will constrain the extrapolations to the high-density domain. In this contribution we introduce a new relativistic effective interaction that is simultaneously constrained by the properties of finite nuclei, their collective excitations, and neutron-star properties. By adjusting two of the empirical parameters of the theory, one can efficiently tune the neutron skin thickness of {sup 208}Pb and the maximum neutron-star mass. We illustrate this procedure in response to the recent interpretation of x-ray observations by Steiner, Lattimer, and Brown that suggests that the FSUGold effective interaction predicts neutron-star radii that are too large and a maximum stellar mass that is too small. The new effective interaction is fitted to a neutron skin thickness in {sup 208}Pb of only R{sub n}-R{sub p}=0.16 fm and yields a moderately large maximum neutron-star mass of 1.94 M{sub {center_dot}}.

  14. X-Ray Reprocessing in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.

    2004-01-01

    This is the final report for research entitled "X-ray reprocessing in active galactic nuclei," into X-ray absorption and emission in various classes of active galaxy via X-ray spectral signatures. The fundamental goal of the research was to use these signatures as probes of the central engine structure and circumnuclear environment of active galactic nuclei. The most important accomplishment supported by this grant involved the detailed analysis and interpretation of the XMM data for the bright Seyfert 1 galaxy MCG-6-30-15. This work was performed by Drs. Christopher Reynolds and Mitchell Begelman in collaboration with Dr. Jorn Wilms (University of Tubingen, Germany; PI of the XMM observation) and other European scientists. With XMM we obtained medium resolution X-ray spectra of unprecedented quality for this Seyfert galaxy. Modeling the X-ray spectrum within the framework of accretion disk reflection models produced the first evidence for energy extraction from the spin of a black hole. Specifically, we found that the extreme gravitational redshifts required to explain the X-ray spectrum suggests that the bulk of the energy dissipation is concentrated very close to the black hole, in contrast with the expectations of any pure accretion disk model. In a second paper we addressed the low- energy spectral complexity and used RXTE specta to pin down the high-energy spectral index, thus firming up our initial interpretation. Additionally, we carried out detailed spectral and variability analyses of a number of Seyfert and radio galaxies (e.g., NGC 5548 and 3C 111) and developed general techniques that will be useful in performing X-ray reverberation mapping of accretion disks in AGN, once adequate data becomes available. A list of papers supported by this research is included.

  15. Structure and reactions of drip-line nuclei

    SciTech Connect

    Hansen, P.G.

    1996-12-31

    Secondary radioactive beams produced at intermediate-energy heavy-ion accelerators have in a short time span added a new dimension to the research on nuclear species at the limits of particle stability, and new detection techniques have made it possible to study reactions caused by incident beams of as little as one particle per second. Imminent developments such as the M.S.U. Coupled-Cyclotron Facility are expected to extend the range and to permit the observation of many previously inaccessible species. For a perspective on the progress in this area one only needs to go about fifteen years back to a time when it had just become possible to study the radioactivity of rare nuclear species such as {sup 11}Li. In presenting early experiments with secondary beams produced in fragmentation James Symons said {open_quotes}... In the introduction to this paper we questioned the applicability of high-energy heavy-ion accelerators to this field. Our experience at the Bevalac leads us to believe that this question does indeed have a positive answer. If the physics interest justifies it, then high-energy heavy-ion beams can certainly be expected to play a role in the study of nuclei at the limits of stability.{close_quotes} At the time, very few, if any, realized how prophetic this remark was. In the present paper the interpretation of the longitudinal-momentum distributions from the nuclear fragmentation of single-nucleon halos is discussed. It is pointed out that these measurements, at least for the cases studied so far, directly reflect the halo wave function, and that there is no direct contribution from the reaction mechanism. This is an important difference from the radial momentum distributions, for which diffractive processes play an important role. The author discusses stripping reactions of {sup 11}Be and {sup 8}B on light nuclei yielding {sup 10}Be and {sup 7}Be.

  16. Partitioning sources of variation in vertebrate species richness

    USGS Publications Warehouse

    Boone, R.B.; Krohn, W.B.

    2000-01-01

    Aim: To explore biogeographic patterns of terrestrial vertebrates in Maine, USA using techniques that would describe local and spatial correlations with the environment. Location: Maine, USA. Methods: We delineated the ranges within Maine (86,156 km2) of 275 species using literature and expert review. Ranges were combined into species richness maps, and compared to geomorphology, climate, and woody plant distributions. Methods were adapted that compared richness of all vertebrate classes to each environmental correlate, rather than assessing a single explanatory theory. We partitioned variation in species richness into components using tree and multiple linear regression. Methods were used that allowed for useful comparisons between tree and linear regression results. For both methods we partitioned variation into broad-scale (spatially autocorrelated) and fine-scale (spatially uncorrelated) explained and unexplained components. By partitioning variance, and using both tree and linear regression in analyses, we explored the degree of variation in species richness for each vertebrate group that Could be explained by the relative contribution of each environmental variable. Results: In tree regression, climate variation explained richness better (92% of mean deviance explained for all species) than woody plant variation (87%) and geomorphology (86%). Reptiles were highly correlated with environmental variation (93%), followed by mammals, amphibians, and birds (each with 84-82% deviance explained). In multiple linear regression, climate was most closely associated with total vertebrate richness (78%), followed by woody plants (67%) and geomorphology (56%). Again, reptiles were closely correlated with the environment (95%), followed by mammals (73%), amphibians (63%) and birds (57%). Main conclusions: Comparing variation explained using tree and multiple linear regression quantified the importance of nonlinear relationships and local interactions between species

  17. Interaction of eta mesons with nuclei.

    PubMed

    Kelkar, N G; Khemchandani, K P; Upadhyay, N J; Jain, B K

    2013-06-01

    Back in the mid-1980s, a new branch of investigation related to the interaction of eta mesons with nuclei came into existence. It started with the theoretical prediction of possible exotic states of eta mesons and nuclei bound by the strong interaction and later developed into an extensive experimental program to search for such unstable states as well as understand the underlying interaction via eta-meson producing reactions. The vast literature of experimental as well as theoretical works that studied various aspects of eta-producing reactions such as the π(+)n → ηp, pd → (3)Heη, p (6)Li → (7)Be η and γ (3)He → η X, to name a few, had but one objective in mind: to understand the eta-nucleon (ηN) and hence the η-nucleus interaction which could explain the production data and confirm the existence of some η-mesic nuclei. In spite of these efforts, there remain uncertainties in the knowledge of the ηN and hence the η-nucleus interaction. Therefore, this review is an attempt to bind together the findings in these works and draw some global and specific conclusions which can be useful for future explorations.The ηN scattering length (which represents the strength of the η-nucleon interaction) using different theoretical models and analyzing the data on η production in pion, photon and proton induced reactions was found to be spread out in a wide range, namely, 0.18 ≤ Re aηN ≤ 1.03 fm and 0.16 ≤ Rm aηN ≤ 0.49 fm. Theoretical searches of heavy η-mesic nuclei based on η-nucleus optical potentials and lighter ones based on Faddeev type few-body approaches predict the existence of several quasibound and resonant states. Although some hints of η-mesic states such as (3)(η)He and (25)(η)Mg do exist from previous experiments, the promise of clearer signals for the existence of η-mesic nuclei lies in the experiments to be performed at the J-PARC, MAMI and COSY facilities in the near future. This review is aimed at giving an overall status

  18. Reflection Asymmetric Shapes in the Neutron-Rich 140,143Ba Isotopes

    NASA Astrophysics Data System (ADS)

    Zhu Sheng-jiang (S, J. Zhu; Wang, Mu-ge; J, H. Hamilton; A, V. Ramayya; B, R. S. Babu; W, C. Ma; Long, Gui-lu; Deng, Jing-kang; Zhu, Ling-yan; Li, Ming; T, N. Ginter; J, Komicki; J, D. Cole; R, Aryaeinejad; Y, K. Dardenne; M, W. Drigert; J, O. Rasmussen; Ts, Yu Oganessian; M, A. Stoyer; S, Y. Chu; K, E. Gregorich; M, F. Mohar; S, G. Prussin; I, Y. Lee; N, R. Johnson; F, K. McGowan

    1997-08-01

    Level schemes for the neutron-rich 140,143Ba nuclei have been determined by study of prompt γ-rays in spontaneous fission of 252Cf. The level pattern and enhanced E1 transitions between π = + and π = - bands show reflection asymmetric shapes with simplex quantum number s = +1 in 140Ba and s = ±i in 143Ba, respectively. The octupole deformation stability with spin variation has been discussed.

  19. Coulomb Excitation of Neutron-Rich Cd Isotopes at REX-ISOLDE

    SciTech Connect

    Kroell, Th.; Behrens, T.; Kruecken, R.; Faestermann, T.; Gernhaeuser, R.; Mahgoub, M.; Maierbeck, P.; Habs, D.; Kester, O.; Lutter, R.; Morgan, T.; Pasini, M.; Rudolph, K.; Thirolf, P.; Bildstein, V.; Niedermaier, O.; Scheit, H.; Schwalm, D.; Martin, D.; Warr, N.

    2005-11-21

    We report on the 'safe' Coulomb excitation of neutron-rich Cd isotopes in the vicinity of the doubly magic nucleus 132Sn. The radioactive nuclei have been produced by ISOLDE at CERN and postaccelerated by the REX-ISOLDE facility. The {gamma}-decay of excited states has been detected by the MINIBALL array. Preliminary results for the B(E2) values of 122,124Cd are consistent with expectations from phenomenological systematics.

  20. Lifetimes in neutron-rich fission fragments using the differential recoil distance method

    SciTech Connect

    Kruecken, R.; Chou, W.-T.; Cooper, J. R.; Beausang, C. W.; Barton, C. J.; Caprio, M. A.; Casten, R. F.; Hecht, A. A.; Novak, J. R.; Pietralla, N.

    2001-07-01

    Lifetimes in the neutron-rich nuclei {sup 104}Mo, {sup 110}Ru, and {sup 144}Ba were measured using the differential recoil distance method. The experiment was performed with a {sup 252}Cf fission source inside the New Yale Plunger Device. {gamma} rays were detected by the SPEctrometer for Experiments with Doppler shifts at Yale (SPEEDY) while fission fragments with the appropriate kinematics were detected by an array of photocells.

  1. Study of astrophysical ({alpha}, n) reactions using light-neutron rich radioactive nuclear beams

    SciTech Connect

    Ishiyama, Hironobu; Watanabe, Yutaka; Imai, Nobuaki; Hirayama, Yoshikazu; Miyatake, Hiroari; Tanaka, Masa-Hiko; Yoshikawa, Nobuharu; Jeong, Sunchan; Fuchi, Yoshihide; Katayama, Ichiro; Nomura, Toru; Ishikawa, Tomoko; Das, Suranjan K.; Mizoi, Yutaka; Fukuda, Tomokazu; Hashimoto, Takashi; Nishio, Katsuhisa; Mitsuoka, Shinichi; Ikezoe, Hiroshi; Matsuda, Makoto

    2006-07-12

    A systematic study of astrophysical reaction rates of ({alpha}, n) reactions on light neutron-rich nuclei using low-energy radioactive nuclear beams is in progress at the tandem facility of Japan Atomic Energy Agency. Exclusive measurements of 8Li({alpha}, n)11B and 12B({alpha}, n)15N reaction cross sections have been performed successfully. Their excitation functions together with the experimental method are presented.

  2. The heavy ion composition in 3HE-rich solar flares

    NASA Technical Reports Server (NTRS)

    Mason, G. M.; Reames, D. V.; Hovestadt, D.; Vonrosenvinge, T. T.

    1985-01-01

    The 3He-rich flares show a tendency to be enriched in heavy ions, and that this enrichment covers the charge range through Fe. The discovery of this association was responsible, in part, for the discarding of 3He enrichment models which involved spallation or thermonuclear reactions, since such models were unable to produce heavy nuclei enhancement. Results of a survey of heavy nucleus abundances observed in 66 3He-rich flares which occurred over the period October 1978 to June 1982 are presented.

  3. The photospheric temperatures and composition of very hot He-rich white dwarfs

    NASA Technical Reports Server (NTRS)

    Barstow, M. A.; Holberg, J. B.

    1990-01-01

    Results are reported from a detailed analysis of Exosat observations of six hot He-rich white dwarfs belonging to, or related to, the spectroscopic subclass of PG1159 stars. These objects are thought to evolve directly from O VI type planetary nebulae nuclei and provide an important link in models of white dwarf evolution. When the Exosat data are compared with the predictions of an extensive grid of He-rich model atmospheres, it is possible to obtain temperature estimates for these stars that are much better constrained than previous attempts.

  4. Pseudo Algebraically Closed Extensions

    NASA Astrophysics Data System (ADS)

    Bary-Soroker, Lior

    2009-07-01

    This PhD deals with the notion of pseudo algebraically closed (PAC) extensions of fields. It develops a group-theoretic machinery, based on a generalization of embedding problems, to study these extensions. Perhaps the main result is that although there are many PAC extensions, the Galois closure of a proper PAC extension is separably closed. The dissertation also contains the following subjects. The group theoretical counterpart of pseudo algebraically closed extensions, the so-called projective pairs. Applications to seemingly unrelated subjects, e.g., an analog of Dirichlet's theorem about primes in arithmetic progression for polynomial rings in one variable over infinite fields.

  5. Emission of complex fragments for compound nuclei formed far from the stability line for A{approx}120

    SciTech Connect

    Gomez Del Campo, J.

    1996-10-01

    Experiments and calculations are presented for the emission of complex fragments (Z>2) from compound nuclei around mass 120 and for bombarding energies below 15 MeV/nucleon. It is shown that a strong enhancement in the emission of complex fragments (especially for Z=6) is expected for compound nuclei formed close or at the N=Z line. Several predictions are given that could be tested with the radioactive beams soon to be available. Also results from a recent experiment that utilizes the emission of complex fragments for {gamma}-ray nuclear spectroscopy studies are presented.

  6. Perceptual presence without counterfactual richness.

    PubMed

    Madary, Michael

    2014-01-01

    In this commentary, I suggest that non-visual perceptual modalities provide counterexamples to Seth's claim that perceptual presence depends on counterfactual richness. Then I suggest a modification to Seth's view that is not vulnerable to these counterexamples. PMID:24739124

  7. Structural changes at large angular momentum in neutron-rich Cd,123121

    NASA Astrophysics Data System (ADS)

    Rejmund, M.; Navin, A.; Bhattacharyya, S.; Caamaño, M.; Clément, E.; Delaune, O.; Farget, F.; de France, G.; Jacquot, B.; Lemasson, A.

    2016-02-01

    Prompt γ rays of isotopically identified neutron-rich isotopes of Cd, produced in transfer- and fusion-fission induced by the 238U beam at 6.2 MeV/u on a 9Be target, were measured using the EXOGAM γ -ray detector array and the magnetic spectrometer VAMOS++. New results for the level scheme of Cd,123121, extending to relatively large angular momentum are reported. The energy levels above 2-MeV excitation energy, are found to differ from those observed in lighter isotopes of Cd indicating a change in structure in these more neutron-rich nuclei. These states are not explained by large-scale shell model calculations, that explain well the structure of the underlying Sn isotopes and the neighboring even-A Cd isotopes. The present data, especially for the odd-A nuclei, point to a deficiency in the matrix elements related to the p-n residual interaction and provide a new domain for testing widely used shell model interactions employed for understanding the evolution of structure in neutron-rich nuclei.

  8. Closed Large Cell Clouds

    Atmospheric Science Data Center

    2013-04-19

    article title:  Closed Large Cell Clouds in the South Pacific     ... unperturbed by cyclonic or frontal activity. When the cell centers are cloudy and the main sinking motion is concentrated at cell ...

  9. Decay properties of exotic [ital N][congruent]28 S and Cl nuclei and the [sup 48]Ca/[sup 46]Ca abundance ratio

    SciTech Connect

    Sorlin, O.; Guillemaud-Mueller, D.; Mueller, A.C.; Borrel, V.; Dogny, S.; Pougheon, F. , Centre National de la Recherche Scientifique, F-91406 Orsay ); Kratz, K.; Gabelmann, H.; Pfeiffer, B.; Woehr, A.; Ziegert, W. ); Penionzhkevich, Y.E.; Lukyanov, S.M.; Salamatin, V.S. , P.O. Box 79, Dubna ); Anne, R.; Borcea, C.; Fifield, L.K.; Lewitowicz, M.; Saint-Laurent, M.G. , BP-5027, F-14021 Caen ); Bazin, D. ); Detraz, C. , F-14032 Caen ); Thielemann, F. (Harvard-

    1993-06-01

    Beta-decay half-lives and [beta]-delayed neutron-emission probabilities of the very neutron-rich nuclei [sup 44]S and [sup 45--47]Cl have been measured. These isotopes, which lie at or close to the [ital N]=28 magic shell, were produced in interactions of a 60 MeV/u [sup 48]Ca beam from GANIL (Grand Accelerateur National d'Ions Lourds) with a [sup 64]Ni target, and were separated by the doubly achromatic spectrometer LISE (Ligne d'Ions Super Epluches). Their decay was studied by a [beta]-[ital n] time correlation measurement. The results are compared to recent model predictions and indicate a rapid weakening of the [ital N]=28 shell effect below [sub 20][sup 48]Ca[sub 28]. The nuclear structure effects reflected in the decay properties of the exotic S and Cl isotopes may be the clue for the astrophysical understanding of the unusual [sup 48]Ca/[sup 46]Ca abundance ratio measured in the solar system as well as the Ca-Ti-Cr anomalies observed in E. King inclusions of the Allende meteorite.

  10. An Improved Cluster Richness Estimator

    SciTech Connect

    Rozo, Eduardo; Rykoff, Eli S.; Koester, Benjamin P.; McKay, Timothy; Hao, Jiangang; Evrard, August; Wechsler, Risa H.; Hansen, Sarah; Sheldon, Erin; Johnston, David; Becker, Matthew R.; Annis, James T.; Bleem, Lindsey; Scranton, Ryan; /Pittsburgh U.

    2009-08-03

    Minimizing the scatter between cluster mass and accessible observables is an important goal for cluster cosmology. In this work, we introduce a new matched filter richness estimator, and test its performance using the maxBCG cluster catalog. Our new estimator significantly reduces the variance in the L{sub X}-richness relation, from {sigma}{sub lnL{sub X}}{sup 2} = (0.86 {+-} 0.02){sup 2} to {sigma}{sub lnL{sub X}}{sup 2} = (0.69 {+-} 0.02){sup 2}. Relative to the maxBCG richness estimate, it also removes the strong redshift dependence of the richness scaling relations, and is significantly more robust to photometric and redshift errors. These improvements are largely due to our more sophisticated treatment of galaxy color data. We also demonstrate the scatter in the L{sub X}-richness relation depends on the aperture used to estimate cluster richness, and introduce a novel approach for optimizing said aperture which can be easily generalized to other mass tracers.

  11. Rediscovery of the nucleolinus, a dynamic RNA-rich organelle associated with the nucleolus, spindle, and centrosomes

    PubMed Central

    Alliegro, Mary Anne; Henry, Jonathan J.; Alliegro, Mark C.

    2010-01-01

    The nucleolinus is an RNA-rich compartment, closely apposed to or embedded within the nucleolus. Discovered over 150 y ago, fewer than two dozen articles have been published on the nucleolinus, probably because complex histochemical stains are required for its visualization in the great majority of cells. The nucleolinus has been reported in invertebrate oocytes, mammalian and amphibian epithelial cells, neurons, and several transformed cell lines. A prominent nucleolinus, clearly visible with transmitted light microscopes at 10× magnification, is present in each oocyte of the surf clam, Spisula solidissima. We observed a consistent relationship between the nucleolinus and the developing meiotic apparatus following Spisula oocyte activation. Through sonication and sucrose gradient fractionation of purified oocyte nuclei, we isolated nucleolini, extracted their RNA, and prepared an in situ riboprobe (NLi-1), which is associated specifically with the nucleolinus, confirming its unique composition. Other in situ observations revealed a NLi-1 and nucleolinar association with the developing spindle and centrosomes. Laser microsurgery that targeted the nucleolinus resulted in failed meiotic cell division in parthenogenetically activated oocytes and failed mitosis in fertilized oocytes. Although the nucleolinus may be a forgotten organelle, its demonstrated role in spindle formation suggests it deserves renewed attention. PMID:20643950

  12. Automated Segmentation of Nuclei in Breast Cancer Histopathology Images

    PubMed Central

    Paramanandam, Maqlin; O’Byrne, Michael; Ghosh, Bidisha; Mammen, Joy John; Manipadam, Marie Therese; Thamburaj, Robinson; Pakrashi, Vikram

    2016-01-01

    The process of Nuclei detection in high-grade breast cancer images is quite challenging in the case of image processing techniques due to certain heterogeneous characteristics of cancer nuclei such as enlarged and irregularly shaped nuclei, highly coarse chromatin marginalized to the nuclei periphery and visible nucleoli. Recent reviews state that existing techniques show appreciable segmentation accuracy on breast histopathology images whose nuclei are dispersed and regular in texture and shape; however, typical cancer nuclei are often clustered and have irregular texture and shape properties. This paper proposes a novel segmentation algorithm for detecting individual nuclei from Hematoxylin and Eosin (H&E) stained breast histopathology images. This detection framework estimates a nuclei saliency map using tensor voting followed by boundary extraction of the nuclei on the saliency map using a Loopy Back Propagation (LBP) algorithm on a Markov Random Field (MRF). The method was tested on both whole-slide images and frames of breast cancer histopathology images. Experimental results demonstrate high segmentation performance with efficient precision, recall and dice-coefficient rates, upon testing high-grade breast cancer images containing several thousand nuclei. In addition to the optimal performance on the highly complex images presented in this paper, this method also gave appreciable results in comparison with two recently published methods—Wienert et al. (2012) and Veta et al. (2013), which were tested using their own datasets. PMID:27649496

  13. Automated Segmentation of Nuclei in Breast Cancer Histopathology Images.

    PubMed

    Paramanandam, Maqlin; O'Byrne, Michael; Ghosh, Bidisha; Mammen, Joy John; Manipadam, Marie Therese; Thamburaj, Robinson; Pakrashi, Vikram

    2016-01-01

    The process of Nuclei detection in high-grade breast cancer images is quite challenging in the case of image processing techniques due to certain heterogeneous characteristics of cancer nuclei such as enlarged and irregularly shaped nuclei, highly coarse chromatin marginalized to the nuclei periphery and visible nucleoli. Recent reviews state that existing techniques show appreciable segmentation accuracy on breast histopathology images whose nuclei are dispersed and regular in texture and shape; however, typical cancer nuclei are often clustered and have irregular texture and shape properties. This paper proposes a novel segmentation algorithm for detecting individual nuclei from Hematoxylin and Eosin (H&E) stained breast histopathology images. This detection framework estimates a nuclei saliency map using tensor voting followed by boundary extraction of the nuclei on the saliency map using a Loopy Back Propagation (LBP) algorithm on a Markov Random Field (MRF). The method was tested on both whole-slide images and frames of breast cancer histopathology images. Experimental results demonstrate high segmentation performance with efficient precision, recall and dice-coefficient rates, upon testing high-grade breast cancer images containing several thousand nuclei. In addition to the optimal performance on the highly complex images presented in this paper, this method also gave appreciable results in comparison with two recently published methods-Wienert et al. (2012) and Veta et al. (2013), which were tested using their own datasets. PMID:27649496

  14. Automated Segmentation of Nuclei in Breast Cancer Histopathology Images.

    PubMed

    Paramanandam, Maqlin; O'Byrne, Michael; Ghosh, Bidisha; Mammen, Joy John; Manipadam, Marie Therese; Thamburaj, Robinson; Pakrashi, Vikram

    2016-01-01

    The process of Nuclei detection in high-grade breast cancer images is quite challenging in the case of image processing techniques due to certain heterogeneous characteristics of cancer nuclei such as enlarged and irregularly shaped nuclei, highly coarse chromatin marginalized to the nuclei periphery and visible nucleoli. Recent reviews state that existing techniques show appreciable segmentation accuracy on breast histopathology images whose nuclei are dispersed and regular in texture and shape; however, typical cancer nuclei are often clustered and have irregular texture and shape properties. This paper proposes a novel segmentation algorithm for detecting individual nuclei from Hematoxylin and Eosin (H&E) stained breast histopathology images. This detection framework estimates a nuclei saliency map using tensor voting followed by boundary extraction of the nuclei on the saliency map using a Loopy Back Propagation (LBP) algorithm on a Markov Random Field (MRF). The method was tested on both whole-slide images and frames of breast cancer histopathology images. Experimental results demonstrate high segmentation performance with efficient precision, recall and dice-coefficient rates, upon testing high-grade breast cancer images containing several thousand nuclei. In addition to the optimal performance on the highly complex images presented in this paper, this method also gave appreciable results in comparison with two recently published methods-Wienert et al. (2012) and Veta et al. (2013), which were tested using their own datasets.

  15. Curriculum Construction: A Critical Analysis of Rich Tasks in the Recontextualisation Field

    ERIC Educational Resources Information Center

    Macdonald, Doune; Hunter, Lisa; Tinning, Richard

    2007-01-01

    Within Education Queensland's recent "new basics" curriculum initiative, Education Queensland developed 20 transdisciplinary learning and assessment tasks for Years 1 to 9, called "rich tasks". This paper critiques two of the rich tasks that were most closely aligned to knowledge and skills within the health and physical education learning area.…

  16. Studies of Low Luminosity Active Galactic Nuclei with Monte Carlo and Magnetohydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Hilburn, Guy Louis

    Results from several studies are presented which detail explorations of the physical and spectral properties of low luminosity active galactic nuclei. An initial Sagittarius A* general relativistic magnetohydrodynamic simulation and Monte Carlo radiation transport model suggests accretion rate changes as the dominant flaring method. A similar study on M87 introduces new methods to the Monte Carlo model for increased consistency in highly energetic sources. Again, accretion rate variation seems most appropriate to explain spectral transients. To more closely resolve the methods of particle energization in active galactic nuclei accretion disks, a series of localized shearing box simulations explores the effect of numerical resolution on the development of current sheets. A particular focus on numerically describing converged current sheet formation will provide new methods for consideration of turbulence in accretion disks.

  17. The emergence of deformation and rotational states in the many-nucleon quantum theory of nuclei

    NASA Astrophysics Data System (ADS)

    Rowe, D. J.

    2016-02-01

    The many-nucleon quantum mechanics of a nucleus is infinite-dimensional and, although simply defined, it has the potential for unlimited complexity. Nevertheless, the low-energy states of heavy open-shell nuclei exhibit properties that are remarkably well described by simple collective models. This paper examines this emergent simplicity from a perspective that closely parallels the emergence of shell structure in the Mayer-Jensen model. The result is an expression of the many-nucleon Hilbert space of a nucleus as an energy-ordered sum of subspaces each of which carries a microscopic version of the Bohr-Mottelson unified model. Each of the subspaces is characterized by nuclear states with a common intrinsic shape defined by its quadrupole moments. An emergence of simplicity and shape-coexistence in nuclei is then explained if it can be demonstrated that there is a relatively small and coherent mixing of the states of different collective subspaces.

  18. GDR as a Probe of the Collective Motion in Nuclei at High Spins, Temperatures or Isospins

    SciTech Connect

    Maj, Adam

    2008-11-11

    The gamma-decay of the Giant Dipole Resonance (GDR), the high-frequency collective vibration of protons against neutrons, has been proven to be a basic probe for the shapes of hot nuclei, especially to study the effective shape evolution caused by the collective rotation of a nucleus. In this context an interesting question arises: what is the nuclear shape at extreme values of spin or temperatures, close to the limit impose by another collective motion--fission, and how evolves the giant dipole collective vibrations as a function of isospin. Short overview of the results from the experiments aimed to answer these questions are presented and possible perspectives of these type of studies for exotic nuclei to be obtained with the novel gamma-calorimeter PARIS and soon available intense radioactive beams are discussed.

  19. Systematics of the First 2{sup +} Excitation in Spherical Nuclei with Skyrme-QRPA

    SciTech Connect

    Terasaki, J.

    2009-05-07

    We use the Quasiparticle Random Phase Approximation (QRPA) and the Skyrme interactions SLy4 and SkM* to systematically calculate energies and transition strengths for the lowest 2{sup +} state in spherical even-even nuclei. The SkM* functional, applied to 178 spherical nuclei between Z = 10 and 90, produces excitation energies that are on average 11% higher than experimental values, with residuals that fluctuate about the average by -35%+55%. The predictions of SkM* and SLy4 have significant differences, in part because of differences in the calculated ground state deformations; SkM* performs better in both the average and dispersion of energies. Comparing the QRPA results with those of generator-coordinate-method (GCM) calculations, we find that the QRPA reproduces trends near closed shells better than the GCM, and overpredicts the energies less severely in general.

  20. The Structure of Nuclei Far from Stability

    SciTech Connect

    Zganjar, E.F.

    1999-02-25

    From among a number of important nuclear structure results that have emerged from our research program during the past few years, two stand out as being of extra significance. These are: (a) the identification of a diabatic coexisting structure in {sup 187}Au which arises solely from differences in proton occupation of adjacent oscillator shells, and (b) the realization of a method for estimating EO strength in nuclei and the resulting prediction that the de-excitation of superdeformed bands may proceed, in some cases, by strong EO transitions.

  1. Probing Chiral Interactions in Light Nuclei

    SciTech Connect

    Nogga, A; Barrett, B R; Meissner, U; Witala, H; Epelbaum, E; Kamada, H; Navratil, P; Glockle, W; Vary, J P

    2004-01-08

    Chiral two- and three-nucleon interactions are studied in a few-nucleon systems. We investigate the cut-off dependence and convergence with respect to the chiral expansion. It is pointed out that the spectra of light nuclei are sensitive to the three-nucleon force structure. As an example, we present calculations of the 1{sup +} and 3{sup +} states of {sup 6}Li using the no-core shell model approach. The results show contributions of the next-to-next-to-leading order terms to the spectra, which are not correlated to the three-nucleon binding energy prediction.

  2. Electron capture on iron group nuclei

    SciTech Connect

    Dean, D.J.; Chatterjee, L.; Strayer, M.R.; Dean, D.J.; Chatterjee, L.; Langanke, K.; Chatterjee, L.; Radha, P.B.

    1998-07-01

    We present Gamow-Teller strength distributions from shell model Monte Carlo studies of fp-shell nuclei that may play an important role in the precollapse evolution of supernovas. We then use these strength distributions to calculate the electron-capture cross sections and rates in the zero-momentum transfer limit. We also discuss the thermal behavior of the cross sections. We find large differences in these cross sections and rates when compared to the naive single-particle estimates. These differences need to be taken into account for improved modeling of the early stages of type-II supernova evolution. thinsp {copyright} {ital 1998} {ital The American Physical Society}

  3. Algebraic description of intrinsic modes in nuclei

    SciTech Connect

    Leviatan, A.

    1989-01-01

    We present a procedure for extracting normal modes in algebraic number-conserving systems of interacting bosons relevant for collective states in even-even nuclei. The Hamiltonian is resolved into intrinsic (bandhead related) and collective (in-band related) parts. Shape parameters are introduced through non-spherical boson bases. Intrinsic modes decoupled from the spurious modes are obtained from the intinsic part of the Hamiltonian in the limit of large number of bosons. Intrinsic states are constructed and serve to evaluate electromagnetic transition rates. The method is illustrated for systems with one type of boson as well as with proton-neutron bosons. 28 refs., 1 fig.

  4. Short-Distance Structure of Nuclei

    SciTech Connect

    Douglas Higinbotham, Eliazer Piasetzky, Stephen Wood

    2011-06-01

    One of Jefferson Lab's original missions was to further our understanding of the short-distance structure of nuclei. In particular, to understand what happens when two or more nucleons within a nucleus have strongly overlapping wave-functions; a phenomena commonly referred to as short-range correlations. Herein, we review the results of the (e,e'), (e,e'p) and (e,e'pN) reactions that have been used at Jefferson Lab to probe this short-distance structure as well as provide an outlook for future experiments.

  5. Effective field theory for deformed atomic nuclei

    NASA Astrophysics Data System (ADS)

    Papenbrock, T.; Weidenmüller, H. A.

    2016-05-01

    We present an effective field theory (EFT) for a model-independent description of deformed atomic nuclei. In leading order this approach recovers the well-known results from the collective model by Bohr and Mottelson. When higher-order corrections are computed, the EFT accounts for finer details such as the variation of the moment of inertia with the band head and the small magnitudes of interband E2 transitions. For rotational bands with a finite spin of the band head, the EFT is equivalent to the theory of a charged particle on the sphere subject to a magnetic monopole field.

  6. Exploring the Physics of Unstable Nuclei

    NASA Astrophysics Data System (ADS)

    Volya, Alexander

    In this presentation the Continuum Shell Model (CSM) approach is advertised as a powerful theoretical tool for studying physics of unstable nuclei. The approach is illustrated using 17O as an example, which is followed by a brief presentation of the general CSM formalism. The successes of the CSM are highlighted and references are provided throughout the text. As an example, the CSM is applied perturbatively to 20O allowing one to explore the effects of continuum on positions of weakly bound states and low-lying resonances, as well as to discern some effects of threshold discontinuity.

  7. Quantum Monte Carlo calculations for light nuclei.

    SciTech Connect

    Wiringa, R. B.

    1998-10-23

    Quantum Monte Carlo calculations of ground and low-lying excited states for nuclei with A {le} 8 are made using a realistic Hamiltonian that fits NN scattering data. Results for more than 40 different (J{pi}, T) states, plus isobaric analogs, are obtained and the known excitation spectra are reproduced reasonably well. Various density and momentum distributions and electromagnetic form factors and moments have also been computed. These are the first microscopic calculations that directly produce nuclear shell structure from realistic NN interactions.

  8. Flux of light antimatter nuclei near Earth

    SciTech Connect

    Baret, B.; Barrau, A.; Buenerd, M.; Derome, L.; Duperray, R.; Protasov, K.; Vratogna, S.; Maurin, D.

    2006-07-11

    The fluxes of light antinuclei A{<=} 4 induced near earth by Cosmic Ray (CR) interactions with the interstellar matter (ISM) in the Galaxy are calculated in a phenomenological framework. The hadronic production cross-section for antinucleons is based on a recent parametrization of a wide set of accelerator data. The production of light nuclei is calculated using coalescence models. The non annihilating inelastic scattering process for the antideuterons is discussed and taken into account for the first time via a more realistic procedure than used so far for antiprotons.

  9. Rotational spacings in superdeformed bands of nuclei

    SciTech Connect

    Chasman, R.R.; Farhan, A.

    1995-08-01

    An unexpected result of the experimental investigation of superdeformed rotational bands is the observation of near-identical dynamic moments of inertia in different nuclei. This phenomenon was also noted in normally deformed rotational bands. A priori, the BCS method is suspect at I = 0 for the treatment of superdeformed nuclear shapes because the single-particle level density near the nuclear surface is small. If it were large, there would be no superdeformed minimum. At high spin, pairing correlations are further weakened, and the BCS method becomes even worse.

  10. Cloud condensation nuclei near marine stratus

    NASA Technical Reports Server (NTRS)

    Hudson, James G.; Frisbie, Paul R.

    1991-01-01

    Extensive airborne measurements of cloud condensation nucleus (CCN) spectra and concentrations of total particles, or condensation nuclei (CN), below, in, and above the stratus cloud decks off the southern California coast point to important aerosol-cloud interactions. Consistently low CCN concentrations below cloud appear to be due to cloud scavenging processes which include Brownian coagulation, nucleation, coalescence, and drizzle. The higher CCN and CN concentrations above cloud are associated with ambient ozone concentrations which suggest a link with continental, probably anthropogenic, sources, even at distances of 500 km from the California coast.

  11. Invariant mass spectroscopy of halo nuclei

    SciTech Connect

    Nakamura, Takashi

    2008-11-11

    We have applied the invariant mass spectroscopy to explore the low-lying exited states of halo nuclei at intermediate energies around 70 MeV/nucleon at RIKEN. As examples, we show here the results of Coulomb breakup study for {sup 11}Li using the Pb target, as well as breakup reactions of {sup 14}Be with p and C targets. The former study revealed a strong Coulomb breakup cross section reflecting the large enhancement of E1 strength at low excitation energies (soft E1 excitation). The latter revealed the observation of the first 2{sup +} state in {sup 14}Be.

  12. Self-Consistency Effects In Superheavy Nuclei

    SciTech Connect

    Afanasjev, A.V.; Frauendorf, S.

    2005-04-05

    The influence of the central depression in the density distribution of spherical superheavy nuclei on the shell structure is studied within the relativistic mean field theory. Large depression leads to the shell gaps at the proton Z = 120 and neutron N = 172 numbers, while flatter density distribution favors N = 184 for neutrons and leads to the appearance of a Z 126 shell gap and to the decrease of the size of the Z = 120 shell gap. The correlations between the magic shell gaps and the magnitude of central depression are discussed for relativistic and non-relativistic mean field theories.

  13. Signatures for quark clustering in nuclei

    SciTech Connect

    Carlson, C.E.; Lassila, K.E.

    1994-04-01

    As a signature for the presence of quark clusters in nuclei, the authors suggest studying backward protons produced by electron scattering off deuterons and suggest a ratio that cancels out much of the detailed properties of deuterons or 6-quark clusters. The test may be viewed as a test that the short range part of the deuteron is still a 2-nucleon system. They make estimates to show how it fails in characteristic and significant ways if the two nucleons at short range coalesce into a kneaded 6-quark cluster.

  14. Effective field theory for deformed atomic nuclei

    DOE PAGES

    Papenbrock, Thomas F.; Weidenmüller, H. A.

    2016-04-13

    In this paper, we present an effective field theory (EFT) for a model-independent description of deformed atomic nuclei. In leading order this approach recovers the well-known results from the collective model by Bohr and Mottelson. When higher-order corrections are computed, the EFT accounts for finer details such as the variation of the moment of inertia with the band head and the small magnitudes of interband E2 transitions. Finally, for rotational bands with a finite spin of the band head, the EFT is equivalent to the theory of a charged particle on the sphere subject to a magnetic monopole field.

  15. Nuclear data on unstable nuclei for astrophysics

    NASA Astrophysics Data System (ADS)

    Smith, Michael S.; Meyer, Richard A.; Bardayan, Daniel W.; Blackmon, Jeffery C.; Chae, Kyungyuk; Guidry, Michael W.; Hix, W. Raphael; Kozub, R. L.; Lingerfelt, Eric J.; Ma, Zhanwen; Scott, Jason P.

    2004-12-01

    Recent measurements with radioactive beams at ORNL's Holifield Radioactive Ion Beam Facility (HRIBF) have prompted the evaluation of a number of reactions involving unstable nuclei needed for stellar explosion studies. We discuss these evaluations, as well as the development of a new computational infrastructure to enable the rapid incorporation of the latest nuclear physics results in astrophysics models. This infrastructure includes programs that simplify the generation of reaction rates, manage rate databases, and visualize reaction rates, all hosted at a new website http://www.nucastrodata.org.

  16. Boost covariant gluon distributions in large nuclei

    NASA Astrophysics Data System (ADS)

    McLerran, Larry; Venugopalan, Raju

    1998-04-01

    It has been shown recently that there exist analytical solutions of the Yang-Mills equations for non-Abelian Weizsäcker-Williams fields which describe the distribution of gluons in large nuclei at small x. These solutions however depend on the color charge distribution at large rapidities. We here construct a model of the color charge distribution of partons in the fragmentation region and use it to compute the boost covariant momentum distributions of wee gluons. The phenomenological applications of our results are discussed.

  17. Enhanced subbarrier fusion for proton halo nuclei

    NASA Astrophysics Data System (ADS)

    Kumar, Raj; Lay, J. A.; Vitturi, A.

    2014-02-01

    In this Brief Report we use a simple model to describe the dynamical effects of break-up processes in the subbarrier fusion involving weakly bound nuclei. We model two similar cases involving either a neutron or a proton halo nucleus, both schematically coupled to the break-up channels. We find that the decrease of the Coulomb barrier in the proton break-up channel leads, ceteris paribus, to a larger enhancement of the subbarrier fusion probabilities with respect to the neutron halo case.

  18. Radii of neutron drops probed via the neutron skin thickness of nuclei

    NASA Astrophysics Data System (ADS)

    Zhao, P. W.; Gandolfi, S.

    2016-10-01

    Multineutron systems are crucial to understanding the physics of neutron-rich nuclei and neutron stars. Neutron drops, neutrons confined in an external field, are investigated systematically in both nonrelativistic and relativistic density functional theories and with ab initio calculations. We demonstrate a new strong linear correlation, which is universal in the realm of mean-field models, between the rms radii of neutron drops and the neutron skin thickness of 208Pb and 48Ca, i.e., the difference between the neutron and proton rms radii of a nucleus. Due to its high quality, this correlation can be used to deduce the radii of neutron drops from the measured neutron skin thickness in a model-independent way, and the radii obtained for neutron drops can provide a useful constraint for realistic three-neutron forces. We also present a new correlation between the slope L of the symmetry energy and the radii of neutron drops, and provide the first validation of such a correlation by using density-functional models and ab initio calculations. These newly established correlations, together with more precise measurements of the neutron skin thicknesses of 208Pb and 48Ca and/or accurate determinations of L , will have an enduring impact on the understanding of multineutron interactions, neutron-rich nuclei, neutron stars, etc.

  19. Approaching the precursor nuclei of the third r-process peak with RIBs

    NASA Astrophysics Data System (ADS)

    Domingo-Pardo, C.; Caballero-Folch, R.; Agramunt, J.; Algora, A.; Arcones, A.; Ameil, F.; Ayyad, Y.; Benlliure, J.; Bowry, M.; Calviño, F.; Cano-Ott, D.; Cortés, G.; Davinson, T.; Dillmann, I.; Estrade, A.; Evdokimov, A.; Faestermann, T.; Farinon, F.; Galaviz, D.; García-Rios, A.; Geissel, H.; Gelletly, W.; Gernhäuser, R.; Gómez-Hornillos, M. B.; Guerrero, C.; Heil, M.; Hinke, C.; Knöbel, R.; Kojouharov, I.; Kurcewicz, J.; Kurz, N.; Litvinov, Y.; Maier, L.; Marganiec, J.; Marta, M.; Martínez, T.; Martínez-Pinedo, G.; Meyer, B. S.; Montes, F.; Mukha, I.; Napoli, D. R.; Nociforo, Ch; Paradela, C.; Pietri, S.; Podolyák, Z.; Prochazka, A.; Rice, S.; Riego, A.; Rubio, B.; Schaffner, H.; Scheidenberger, Ch; Smith, K.; Sokol, E.; Steiger, K.; Sun, B.; Taín, J. L.; Takechi, M.; Testov, D.; Weick, H.; Wilson, E.; Winfield, J. S.; Wood, R.; Woods, P.; Yeremin, A.

    2016-01-01

    The rapid neutron nucleosynthesis process involves an enormous amount of very exotic neutron-rich nuclei, which represent a theoretical and experimental challenge. Two of the main decay properties that affect the final abundance distribution the most are half-lives and neutron branching ratios. Using fragmentation of a primary 238U beam at GSI we were able to measure such properties for several neutron-rich nuclei from 208Hg to 218Pb. This contribution provides a short update on the status of the data analysis of this experiment, together with a compilation of the latest results published in this mass region, both experimental and theoretical. The impact of the uncertainties connected with the beta-decay rates and with beta-delayed neutron emission is illustrated on the basis of r-process network calculations. In order to obtain a reasonable reproduction of the third r-process peak, it is expected that both half-lives and neutron branching ratios are substantially smaller, than those based on FRDM+QRPA, commonly used in r-process model calculations. Further measurements around N ∼ 126 are required for a reliable modelling of the underlying nuclear structure, and for performing more realistic r-process abundance calculations.

  20. Unsupervised segmentation of overlapped nuclei using Bayesian classification.

    PubMed

    Jung, Chanho; Kim, Changick; Chae, Seoung Wan; Oh, Sukjoong

    2010-12-01

    In a fully automatic cell extraction process, one of the main issues to overcome is the problem related to extracting overlapped nuclei since such nuclei will often affect the quantitative analysis of cell images. In this paper, we present an unsupervised Bayesian classification scheme for separating overlapped nuclei. The proposed approach first involves applying the distance transform to overlapped nuclei. The topographic surface generated by distance transform is viewed as a mixture of Gaussians in the proposed algorithm. In order to learn the distribution of the topographic surface, the parametric expectation-maximization (EM) algorithm is employed. Cluster validation is performed to determine how many nuclei are overlapped. Our segmentation approach incorporates a priori knowledge about the regular shape of clumped nuclei to yield more accurate segmentation results. Experimental results show that the proposed method yields superior segmentation performance, compared to those produced by conventional schemes.