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Sample records for coexisting nuclear shapes

  1. Nuclear shapes: from earliest ideas to multiple shape coexisting structures

    NASA Astrophysics Data System (ADS)

    Heyde, K.; Wood, J. L.

    2016-08-01

    The concept of the atomic nucleus being characterized by an intrinsic property such as shape came as a result of high precision hyperfine studies in the field of atomic physics, which indicated a non-spherical nuclear charge distribution. Herein, we describe the various steps taken through ingenious experimentation and bold theoretical suggestions that mapped the way for later work in the early 50s by Aage Bohr, Ben Mottelson and James Rainwater. We lay out a long and winding road that marked, in the period of 50s to 70s, the way shell-model and collective-model concepts were reconciled. A rapid increase in both accelerator and detection methods (70s towards the early 2000s) opened new vistas into nuclear shapes, and their coexistence, in various regions of the nuclear mass table. Next, we outline a possible unified view of nuclear shapes: emphasizing decisive steps taken as well as questions remaining, next to the theoretical efforts that could result in an emerging understanding of nuclear shapes, building on the nucleus considered as a strongly interacting system of nucleons as the microscopic starting point.

  2. Coexistence of nuclear shapes: self-consistent mean-field and beyond

    NASA Astrophysics Data System (ADS)

    Li, Z. P.; Nikšić, T.; Vretenar, D.

    2016-02-01

    A quantitative analysis of the evolution of nuclear shapes and shape phase transitions, including regions of short-lived nuclei that are becoming accessible in experiments at radioactive-beam facilities, necessitate accurate modeling of the underlying nucleonic dynamics. Important theoretical advances have recently been made in studies of complex shapes and the corresponding excitation spectra and electromagnetic decay patterns, especially in the ‘beyond mean-field’ framework based on nuclear density functionals. Interesting applications include studies of shape evolution and coexistence in N = 28 isotones, the structure of lowest 0+ excitations in deformed N ≈ 90 rare-earth nuclei, and quadrupole and octupole shape transitions in thorium isotopes.

  3. Nuclear shape coexistence in Po isotopes: An interacting boson model study

    NASA Astrophysics Data System (ADS)

    García-Ramos, J. E.; Heyde, K.

    2015-09-01

    Background: The lead region, Po, Pb, Hg, and Pt, shows up the presence of coexisting structures having different deformation and corresponding to different particle-hole configurations in the shell-model language. Purpose: We intend to study the importance of configuration mixing in the understanding of the nuclear structure of even-even Po isotopes, where the shape coexistence phenomena are not clear enough. Method: We study in detail a long chain of polonium isotopes, Po-208190, using the interacting boson model with configuration mixing (IBM-CM). We fix the parameters of the Hamiltonians through a least-squares fit to the known energies and absolute B (E 2 ) transition rates of states up to 3 MeV. Results: We obtained the IBM-CM Hamiltonians and we calculate excitation energies, B (E 2 ) 's, electric quadrupole moments, nuclear radii and isotopic shifts, quadrupole shape invariants, wave functions, and deformations. Conclusions: We obtain a good agreement with the experimental data for all the studied observables and we conclude that shape coexistence phenomenon is hidden in Po isotopes, very much as in the case of the Pt isotopes.

  4. Nuclear shape coexistence and shape evolution in the A = 155 transitional region

    NASA Astrophysics Data System (ADS)

    Brown, Timothy Bannon

    High-spin states of the rare-earth nuclei 153Gd, 155Dy, and 157Tm were populated using heavy-ion reactions at the Florida State University (FSU) tandem-linac, the Lawrence Berkeley National Laboratory (LBNL) 88' cyclotron and the Holifield Heavy Ion Research Facility at Oak Ridge National Laboratory. The de- exciting γ rays were detected with the Pittsburgh- Florida State Universities array (FSU), the Gammasphere spectrometer (LBNL) or the Oak Ridge Compton-Suppressed γ array. Over 500 new transitions and 300 new levels were identified in the three odd-A nuclei. In each of these nuclei, DCO measurements, rotational alignment behavior, and B(M1)/B(E2) transition strength ratios were analyzed. Cranked Shell Model calculations were performed and compared to the observed behavior in all the nuclei. At high spin in 155Dy and 157Tm, shape evolution via band termination is studied and the experimental data is compared with various high spin cranking calculations. In 155Dy, evidence for shape coexistence at high spin (I > 30/hbar) is discussed. In addition, superdeformed structures have been observed for the first time in the doubly-odd nucleus 130Pr (Z = 59). These latter bands were produced in a heavy-ion reaction at the LBNL 88' cyclotron facility and detected with the Gamma-sphere spectrometer and the Microball charged particle array. Possible quasiparticle assignments are given and extracted B(M1)/B(E2) ratios are consistent with large deformation.

  5. Shape Coexistence in 69Co

    NASA Astrophysics Data System (ADS)

    Puentes, Daniel; Crider, Benjamin; Prokop, Chris; Liddick, Sean

    2016-09-01

    The rapid change in nuclear properties with the addition or removal of a few nucleons can provide a wealth of information on nuclear structure. One such example of rapid changes is shape coexistence which has been observed in numerous regions of the nuclear chart. Evidence for coexistence between normal and deformed configurations in the vicinity of the Ni isotopes near N = 40 has been identified in various isotopes of Co, Ni, and Cu. Levels attributed to the cross-shell proton excitations have been observed as a function of neutron number in all three isotopic chain and are observed to systematically decrease in energy with increasing neutron number. Recently, two β-decaying states in 2769Cohave been identified. However, their relative energy separation is unknown and there are some suggestions that the deformed configuration is the ground state. Observance of a weak γ-ray would, at a minimum, fix the energy difference between the two states of 2769Co.However, the search for the γ-ray transition is difficult due to the long half-life of 750-ms, a strong competition from β decay, and possibly high conversion coefficient. Observance would allow for a better understanding of the systematics of deformation in the Ni region as a function of neutron number.

  6. Shape coexistence in 153Ho

    NASA Astrophysics Data System (ADS)

    Pramanik, Dibyadyuti; Sarkar, S.; Saha Sarkar, M.; Bisoi, Abhijit; Ray, Sudatta; Dasgupta, Shinjinee; Chakraborty, A.; Krishichayan, Kshetri, Ritesh; Ray, Indrani; Ganguly, S.; Pradhan, M. K.; Ray Basu, M.; Raut, R.; Ganguly, G.; Ghugre, S. S.; Sinha, A. K.; Basu, S. K.; Bhattacharya, S.; Mukherjee, A.; Banerjee, P.; Goswami, A.

    2016-08-01

    The high-spin states in 153Ho have been studied by the La57(20Ne139,6 n ) reaction at a projectile energy of 139 MeV at the Variable Energy Cyclotron Centre (VECC), Kolkata, India, utilizing an earlier campaign of the Indian National Gamma Array (INGA) setup. Data from γ -γ coincidence, directional correlation, and polarization measurements have been analyzed to assign and confirm the spins and parities of the levels. We have suggested a few additions and revisions of the reported level scheme of 153Ho. The RF-γ time difference spectra have been useful to confirm the half-life of an isomer in this nucleus. From the comparison of experimental and theoretical results, it is found that there are definite indications of shape coexistence in this nucleus. The experimental and calculated lifetimes of several isomers have been compared to follow the coexistence and evolution of shape with increasing spin.

  7. Shape coexistence: the shell model view

    NASA Astrophysics Data System (ADS)

    Poves, A.

    2016-02-01

    We shall discuss the meaning of the ‘nuclear shape’ in the laboratory frame proper to the spherical shell model. A brief historical promenade will bring us from Elliott’s SU3 breakthrough to today’s large scale shell model calculations. A section is devoted to the algebraic model which extends drastically the field of applicability of Elliot’s SU3, providing a precious heuristic guidance for the exploration of collectivity in the nuclear chart. Shape coexistence and shape mixing will be shown to occur as the result of the competition between the main actors in the nuclear dynamics; the spherical mean field, and the pairing and quadrupole-quadrupole interactions. These ideas will be illustrated with examples in magic nuclei (40Ca and 68Ni); neutron rich semi-magic (32Mg, and 64Cr); and in proton rich N = Z (72Kr).

  8. Shape coexistence in 68Ni

    NASA Astrophysics Data System (ADS)

    Suchyta, S.; Liddick, S.; Bennet, M.; Larson, N.; Prokop, C.; Quinn, S.; Spyrou, A.; Chemey, A.; Simon, A.; Otsuka, T.; Tsunoda, Y.; Shimizu, N.; Honma, M.; Utsuno, Y.; Tripath, V.; Vonmoss, J.

    2013-10-01

    68 Ni has been a focus of recent work aiming to understand the apparent rapid development of collectivity along neutron-rich N = 40 nuclei, but despite many studies, is not entirely understood. The decay of the first excited 0+ state in 68Ni was investigated at the NSCL. Ions of 68Co were implanted into a planar germanium double-sided strip detector (GeDSSD). The beta decay of 68Co populated the first excited 0+ state in 68Ni and within hundreds of nanoseconds the decay of the first excited 0+ state was measured in the GeDSSD. Both the energy of the first excited 0+ state and the electric monopole transition strength from the first excited 0+ state were precisely determined. Comparisons to Monte Carlo Shell Model calculations suggest shape coexistence between spherical ground and oblate first excited 0+ states in 68Ni. The experimental results and theoretical interpretation will be presented.

  9. 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).

  10. Penning-trap mass spectrometry and mean-field study of nuclear shape coexistence in the neutron-deficient lead region

    NASA Astrophysics Data System (ADS)

    Manea, V.; Ascher, P.; Atanasov, D.; Barzakh, A. E.; Beck, D.; Blaum, K.; Borgmann, Ch.; Breitenfeldt, M.; Cakirli, R. B.; Cocolios, T. E.; Day Goodacre, T.; Fedorov, D. V.; Fedosseev, V. N.; George, S.; Herfurth, F.; Kowalska, M.; Kreim, S.; Litvinov, Yu. A.; Lunney, D.; Marsh, B.; Neidherr, D.; Rosenbusch, M.; Rossel, R. E.; Rothe, S.; Schweikhard, L.; Wienholtz, F.; Wolf, R. N.; Zuber, K.

    2017-05-01

    We present a study of nuclear shape coexistence in the region of neutron-deficient lead isotopes. The midshell gold isotopes 180,185,188,190Au (Z =79 ), the two long-lived nuclear states in 197At (Z =85 ), and the neutron-rich nuclide 219At were produced by the ISOLDE facility at CERN and their masses were determined with the high-precision Penning-trap mass spectrometer ISOLTRAP. The studied gold isotopes address the trend of binding energies in a region of the nuclear chart where the nuclear charge radii show pronounced discontinuities. Significant deviations from the atomic-mass evaluation were found for Au,190188. The new trend of two-neutron separation energies is smoother, although it does reveal the onset of deformation. The origin of this effect is interpreted in connection to the odd-even staggering of binding energies, as well as theoretically by Hartree-Fock-Bogoliubov calculations including quasiparticle blocking. The role of blocking for reproducing the large odd-even staggering of charge radii in the mercury isotopic chain is illustrated.

  11. Shape coexistence in Ni68

    NASA Astrophysics Data System (ADS)

    Suchyta, S.; Liddick, S. N.; Tsunoda, Y.; Otsuka, T.; Bennett, M. B.; Chemey, A.; Honma, M.; Larson, N.; Prokop, C. J.; Quinn, S. J.; Shimizu, N.; Simon, A.; Spyrou, A.; Tripathi, V.; Utsuno, Y.; VonMoss, J. M.

    2014-02-01

    The internal-conversion and internal-pair-production decays of the first excited 0+ state in Ni68 are studied following the β decay of Co68. A novel experimental technique, in which the ions of Co68 were implanted into a planar germanium double-sided strip detector and which required digital pulse processing, is developed. The values for the energy of the first excited 0+ state and the electric monopole transition strength from the first excited 0+ state to the ground state in Ni68 are determined to be 1605(3) keV and 7.6(4)×10-3, respectively. Comparisons of the experimental results to Monte Carlo shell-model calculations suggest the coexistence between a spherical ground state and an oblate first excited 0+ state in Ni68.

  12. Shape coexistence along N = 40

    SciTech Connect

    Liddick, S. N.; Suchyta, S.; Abromeit, B.; Ayres, A; Bey, A.; Bingham, C. R.; Bolla, M; Carpenter, M. P.; Cartegni, L.; Chiara, C. J.; Crawford, H. L.; Darby, I. G.; Grzywacz, R.; Gurdal, G.; Ilyushkin, S.; Larson, N.; Madurga, M; McCutchan, E. A.; Miller, D; Padgett, Stephen; Paulauskas, S.; Pereira, J.; Rajabali, M. M.; Rykaczewski, Krzysztof Piotr; Vinnikova, S.; Walters, W. B.; Zhu, S.

    2011-01-01

    The low-energy level structures of 64 25Mn39 and 66 25Mn41 were investigated through both the decay of Mn metastable states and the population of levels following the decay of 64Cr and 66Cr. The deduced level schemes and tentatively assigned spins and parities suggest the coexistence of spherical and deformed configurations above and below N = 40 for the odd-odd Mn isotopes. The low-energy deformed configurations are attributed to the coupling between a proton in a K = 1/2 level with neutrons in either the K = 1/2 or K = 3/2+ levels originating from the p3/2, p1/2, and g9/2 single-particle states, respectively.

  13. Shape Coexistence In Light Krypton Isotopes

    SciTech Connect

    Clement, E.; Goergen, A.; Bouchez, E.; Chatillon, A.; Korten, W.; Le Coz, Y.; Theisen, Ch.; Huerstel, A.; Lucas, R.; Wilson, J.N.; Becker, F.; Gerl, J.; Blank, B.; Hannachi, F.

    2005-04-05

    Shape coexistence in the light krypton isotopes was studied in a series of experiments at GANIL using various experimental techniques. A new low-lying 0+ state, a so-called shape isomer, was found in delayed conversion-electron spectroscopy after fragmentation reactions. The systematics of such low-lying 0+ states suggests that the ground states of the isotopes 78Kr and 76Kr have prolate deformation, while states with prolate and oblate shape are practically degenerate and strongly mixed in 74Kr, and that the oblate configuration becomes the ground state in 72Kr. This scenario was tested in experiments performing low-energy Coulomb excitation of radioactive 76Kr and 74Kr beams from the SPIRAL facility. Both transitional and diagonal electromagnetic matrix elements were extracted from the observed {gamma}-ray yields. The results find the prolate shape for the ground-state bands in 76Kr and 74Kr and an oblate deformation for the excited 2{sub 2}{sup +} state in 74Kr, confirming the proposed scenario of shape coexistence.

  14. Deformed Structures and Shape Coexistence in Zr-98

    NASA Astrophysics Data System (ADS)

    Olaizola, Bruno; 8pi Collaboration

    2015-10-01

    The nuclear structure of the zirconium isotopes evolves from a mid-open neutron shell deformed region (80Zr), through a closed shell (90Zr), to a closed subshell (96Zr), and then to a sudden reappearance of deformation (100Zr). This rapid onset of deformation across the Zr isotopes is unprecedented, and the issue of how collectivity appears and disappears in these isotopes is of special interest. Until recently, only 98Zr (and maybe 100Zr) had indirect and weak evidence for shape coexistence, with only speculative interpretation of the experiments. Recent results from high precision B(E2) measurements provided direct evidence of shape coexistence in 94Zr and suggested that it may happen in many other nuclei in this region. In order to provide direct evidence of shape coexistence in 98Zr a high-statistical-quality γγ experiment was carried out with the 8 π spectrometer at ISAC-TRIUMF. The array consists of 20 Compton-suppressed hyper-pure germanium detectors plus β particle and conversion electron detectors. Excited states up to ~ 5 MeV in 98Zr were populated in the β- decay of 98Y Jπ = (0-) and 98mY J = (4,5). Preliminary results on key branching ratios will be presented. This work was supported by the Natural Sciences and Engineering Research Council of Canada and the National Research Council of Canada.

  15. Shape coexistence from lifetime and branching-ratio measurements in 68,70Ni

    NASA Astrophysics Data System (ADS)

    Crider, B. P.; Prokop, C. J.; Liddick, S. N.; Al-Shudifat, M.; Ayangeakaa, A. D.; Carpenter, M. P.; Carroll, J. J.; Chen, J.; Chiara, C. J.; David, H. M.; Dombos, A. C.; Go, S.; Grzywacz, R.; Harker, J.; Janssens, R. V. F.; Larson, N.; Lauritsen, T.; Lewis, R.; Quinn, S. J.; Recchia, F.; Spyrou, A.; Suchyta, S.; Walters, W. B.; Zhu, S.

    2016-12-01

    Shape coexistence near closed-shell nuclei, whereby states associated with deformed shapes appear at relatively low excitation energy alongside spherical ones, is indicative of the rapid change in structure that can occur with the addition or removal of a few protons or neutrons. Near 68Ni (Z = 28, N = 40), the identification of shape coexistence hinges on hitherto undetermined transition rates to and from low-energy 0+ states. In 68,70Ni, new lifetimes and branching ratios have been measured. These data enable quantitative descriptions of the 0+ states through the deduced transition rates and serve as sensitive probes for characterizing their nuclear wave functions. The results are compared to, and consistent with, large-scale shell-model calculations which predict shape coexistence. With the firm identification of this phenomenon near 68Ni, shape coexistence is now observed in all currently accessible regions of the nuclear chart with closed proton shells and mid-shell neutrons.

  16. Shape coexistence in neutron deficient Po nuclei

    SciTech Connect

    Helariutta, K.; Cocks, J. F. C.; Enqvist, T.; Greenlees, P. T.; Jones, P.; Julin, R.; Juutinen, S.; Jaemsen, P.; Kankaanpaeae, H.; Kettunen, H.; Kuusiniemi, P.; Leino, M.; Muikku, M.; Piiparinen, M.; Rahkila, P.; Savelius, A.; Trzaska, W. H.; Toermaenen, S.; Uusitalo, J.; Allatt, R. G.

    1999-11-16

    The excited levels in {sup 192-195}Po have been studied using the recoil-decay tagging method. New levels have been identified. The data are in accordance with the scheme of the coexisting spherical and deformed intruder structures crossing each other with N<112.

  17. Shape Coexistence in Neutron Deficient Po Nuclei

    SciTech Connect

    Helariutta, K.; Cocks, J.F.C.; Enqvist, T.; Greenlees, P.T.; Jones, P.; Julin, R.; Juutinen, S.; Jamsen, P.; Kankaanpaa, H.; Kettunen, H.; Kuiusiniemi, P.; Leino, M.; Muikkui, M.; Piiparinen, M.; Rahkila, P.; Savelius, A.; Trzaska, W.H.; Tormanen, S.; Uusitalo, J.; Allatt, R.G.; Butler, P.A.; Page, R.D.; Kapusta, M.

    1999-12-31

    The excited levels in {sup 192-195}Po have been studied using the recoil-decay tagging method. New levels have been identified. The data are in accordance with the scheme of the coexisting spherical and deformed intruder structures crossing each other with N<112.

  18. Exotic Nuclear Shapes:

    NASA Astrophysics Data System (ADS)

    Dudek, J.; Schunck, N.; Dubray, N.; Góźdź, A.

    After recalling some in principle known but seldom mentioned facts about variety of concepts/notions of the nuclear shapes, we briefly summarize the results of the recent microscopic calculations predicting the existence of the large-elongation (hyper-deformed) nuclear configurations — as well as another series of calculations predicting that some nuclei should exhibit high-rank symmetries: the tetrahedral and the octahedral ones. The latter are associated with 48- and 96- symmetry elements, respectively, of the nuclear mean-field Hamiltonian. Obviously the physics motivations behind the hyper-deformation and the high-rank symmetry studies are not the observations of the new geometrical forms as such; in our opinion these motivations are much deeper and are given in the text.

  19. Nuclear shape isomers

    NASA Astrophysics Data System (ADS)

    Möller, P.; Sierk, A. J.; Bengtsson, R.; Sagawa, H.; Ichikawa, T.

    2012-03-01

    We calculate potential-energy surfaces as functions of spheroidal (ɛ2), hexadecapole (ɛ4), and axial-asymmetry (γ) shape coordinates for 7206 nuclei from A=31 to A=290. We tabulate the deformations and energies of all minima deeper than 0.2 MeV and of the saddles between all pairs of minima. The tabulation is terminated at N=160. Our study is based on the FRLDM macroscopic-microscopic model defined in ATOMIC DATA AND NUCLEAR DATA TABLES [P. Möller, J.R. Nix, W.D. Myers, W.J. Swiatecki, At. Data Nucl. Data Tables 59 (1995) 185]. We also present potential-energy contour plots versus ɛ2 and γ for 1224 even-even nuclei in the region studied. We can identify nuclei for which a necessary condition for shape isomers occurs, namely multiple minima in the calculated potential-energy surface. We find that the vast majority of nuclear shape isomers occur in the A=80 region, the A=100 region, and in a more extended region centered around 208Pb. A calculated region of shape isomers that has so far not been extensively explored is the region of neutron-deficient actinides "north-east" of 208Pb.

  20. Shape coexistence and phase transitions in the platinum isotopes

    SciTech Connect

    Morales, Irving O.; Frank, Alejandro; Vargas, Carlos E.; Isacker, P. Van

    2008-08-15

    The matrix coherent-state approach of the interacting boson model with configuration mixing is used to study the geometry of the platinum isotopes. With a parameter set determined in previous studies, it is found that the absolute minimum of the potential for the Pt isotopes evolves from spherical to oblate and finally to prolate shapes when the neutron number decreases from N=126 (semi-magic) to N=104 (mid-shell). Shape coexistence is found in the isotopes {sup 182,184,186,188}Pt. A phase diagram is constructed that shows the coexistence region as a function of the number of bosons and the strength of the mixing parameter.

  1. Lifetime measurements and shape coexistence in {sup 144}Dy

    SciTech Connect

    Procter, M. G.; Cullen, D. M.; Niclasen, B.; Mason, P. J. R.; Rigby, S. V.; Dare, J. A.; Lumley, N. M.; Scholey, C.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nyman, M.; Puurunen, A.; Rahkila, P.; Ruotsalainen, P.; Saren, J.

    2010-05-15

    The known level scheme of {sup 144}Dy has been extended and lifetime measurements have been made with the recoil-distance Doppler-shift method. Reduced transition probabilities and deformations have been determined for four low-lying transitions. These states form part of the first observed band crossing, giving information on the change in nuclear deformation resulting from the rearrangement of h{sub 11/2} protons in the nucleus. Two bands built upon excited 10{sup +} states have been assigned pi(h{sub 11/2}){sup 2} prolate and nu(h{sub 11/2}){sup -2} oblate configurations with tau=12(2)ps and 0.01shape coexistence at low energy and moderate spin. A known four-quasiparticle dipole band has been extended to higher spin and lifetime measurements suggest a long-lived bandhead state. In this case, the excited states in the band may be consistent with a shears model interpretation of a magnetic dipole rotor. However, the measured B(M1)/B(E2) branching ratios reveal a larger than expected deformed rotational component compared with that in the analogous band in the lower mass isotone {sup 142}Gd.

  2. Lifetime measurements and shape coexistence in Dy144

    NASA Astrophysics Data System (ADS)

    Procter, M. G.; Cullen, D. M.; Scholey, C.; Niclasen, B.; Mason, P. J. R.; Rigby, S. V.; Dare, J. A.; Dewald, A.; Greenlees, P. T.; Iwasaki, H.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Lumley, N. M.; Möller, O.; Nyman, M.; Peura, P.; Pissulla, T.; Puurunen, A.; Rahkila, P.; Rother, W.; Ruotsalainen, P.; Sarén, J.; Sorri, J.; Uusitalo, J.

    2010-05-01

    The known level scheme of Dy144 has been extended and lifetime measurements have been made with the recoil-distance Doppler-shift method. Reduced transition probabilities and deformations have been determined for four low-lying transitions. These states form part of the first observed band crossing, giving information on the change in nuclear deformation resulting from the rearrangement of h11/2 protons in the nucleus. Two bands built upon excited 10+ states have been assigned π(h11/2)2 prolate and ν(h11/2)-2 oblate configurations with τ=12(2)ps and 0.01<τ≲16ns, respectively. These long lifetimes are reasoned to be a result of shape coexistence at low energy and moderate spin. A known four-quasiparticle dipole band has been extended to higher spin and lifetime measurements suggest a long-lived bandhead state. In this case, the excited states in the band may be consistent with a shears model interpretation of a magnetic dipole rotor. However, the measured B(M1)/B(E2) branching ratios reveal a larger than expected deformed rotational component compared with that in the analogous band in the lower mass isotone Gd142.

  3. Shape coexistence from lifetime and branching-ratio measurements in 68,70Ni

    DOE PAGES

    Crider, B. P.; Prokop, C. J.; Liddick, S. N.; ...

    2016-10-15

    Shape coexistence near closed-shell nuclei, whereby states associated with deformed shapes appear at relatively low excitation energy alongside spherical ones, is indicative of the rapid change in structure that can occur with the addition or removal of a few protons or neutrons. Near 68Ni (Z=28, N=40), the identification of shape coexistence hinges on hitherto undetermined transition rates to and from low-energy 0+ states. In 68,70Ni, new lifetimes and branching ratios have been measured. These data enable quantitative descriptions of the 0+ states through the deduced transition rates and serve as sensitive probes for characterizing their nuclear wave functions. The resultsmore » are compared to, and consistent with, large-scale shell-model calculations which predict shape coexistence. With the firm identification of this phenomenon near 68Ni, shape coexistence is now observed in all currently accessible regions of the nuclear chart with closed proton shells and mid-shell neutrons.« less

  4. Shape coexistence and shell evolution in the 68Ni region

    NASA Astrophysics Data System (ADS)

    Chiara, C. J.

    2016-09-01

    Studies of nuclei along or near the line of stability have long since demonstrated the existence of certain magic numbers of protons or neutrons, corresponding to shell closures where there are large energy gaps among the single-particle orbitals. Nuclei located near these magic numbers tend to have increased stability compared to their neighbors and are typically spherical in their ground states. As technological advances continue to push our reach to nuclei farther from stability, mounting evidence has revealed that this familiar shell structure changes with increasing asymmetry in the numbers of neutrons and protons. The disappearance of some well-known magic numbers and the formation of new ones, driven largely by the tensor force, have both been identified. Along with this shell evolution as a function of nucleon number, a different type can also occur within a given nucleus as a consequence of configuration changes and the corresponding effect of their associated nuclear forces. This latter type of shell evolution manifests itself as a coexistence of spherical and deformed shapes at low excitation energies. Highlights will be presented of recent research on shell evolution in neutron-rich nuclei in the vicinity of 68Ni. Particular emphasis will be given to the efforts at Argonne National Laboratory and the National Superconducting Cyclotron Laboratory which have revealed new structure in these nuclei through multinucleon-transfer reactions and beta-decay spectroscopy. These experimental results could only be explained by concurrent advances in the corresponding shell-model description, requiring larger model spaces than could previously be accommodated. Supported by the US Army Research Lab under Cooperative Agreement W911NF-12-2-0019.

  5. Shape coexistence and the role of axial asymmetry in 72,76Ge

    NASA Astrophysics Data System (ADS)

    Ayangeakaa, A. D.; Janssens, R. V. F.; Wu, C. Y.; Allmond, J. M.; Wood, J. L.; Zhu, S.; Albers, M.; Almaraz-Calderon, S.; Bucher, B.; Carpenter, M. P.; Chiara, C. J.; Cline, D.; Crawford, H. L.; David, H. M.; Harker, J.; Hayes, A. B.; Hoffman, C. R.; Kay, B. P.; Kolos, K.; Korichi, A.; Lauritsen, T.; Macchiavelli, A. O.; Richards, A.; Seweryniak, D.; Wiens, A.

    2016-09-01

    The structure of low-lying states in medium-mass germanium isotopes 72Ge and 76Ge is investigated via projectile Coulomb excitation with GRETINA and CHICO2. In both nuclei, complete sets of E 2 matrix elements were determined and substantial evidence for triaxiality and shape coexistence, based on the model-independent shape invariants deduced from the Kumar-Cline sum rule, has been observed [3]. These observations are supported by results of a two-state mixing model as well as multi-configuration mixing calculations carried out within the framework of the triaxial rotor model. These observations and the role of axial asymmetry in the shape coexistence phenomena, as well as results pertaining to rigid triaxiality in 76Ge will be presented. Department of Energy, Office of Science, Office of Nuclear Physics and the National Science Foundation.

  6. Shape Coexistence in Neutron-Rich Nickel Isotopes around N = 40

    NASA Astrophysics Data System (ADS)

    Prokop, C. J.; e14039 Collaboration; e14057 Collaboration

    2015-10-01

    Shape coexistence is a fascinating phenomenon in atomic nuclei characterized by multiple states with different intrinsic shapes coexisting at similar excitation energies. In even-even nuclei, a hallmark of shape coexistence is low-energy 0+ states. In 68Ni, the Monte-Carlo Shell Model (MCSM) employing the A3DA interaction, utilizing the fpg9/2d5 / 2 model space for protons and neutrons, predicts triple shape coexistence with three 0+ states below 3 MeV. Transitioning to 70Ni, the energy of the prolate-deformed 0+ state is predicted to drop precipitously from 2511 to 1525 keV. This is due to strengthening of the attractive νg9 / 2 - πf5 / 2 and repulsive νg9 / 2 - πf7 / 2 monopole interactions of the tensor force altering the effective single-particle energies of the πf7 / 2 and πf5 / 2 single-particle states, thereby reducing the spherical Z = 28 shell gap. Recent beta-decay spectroscopy experiments at the National Superconducting Cyclotron Laboratory (NSCL) have discovered a new excited 0+ state at 1567 keV in 70Ni. This result supports MCSM predictions extending the picture of shape coexistence to 70Ni and demonstrates the importance of the tensor force for describing the nuclear structure of neutron-rich nuclei. Results of the latest NSCL experiments will be presented. Supported by NSF Contract No. PHY-1102511, by the DOE NNSA Award Nos. DE-NA0000979 and DE-FG52-08NA28552, the U.S DOE SC NP Contract No. DE-AC-06CH11357 and Grant Nos. DE-FG02-94ER40834 and DE-FG02-96ER40983, and U.S. ARL Coop. Agreement W911NF-12-2-0019.

  7. The coexistence curve of finite charged nuclear matter

    NASA Astrophysics Data System (ADS)

    Elliott, J. B.; Moretto, L. G.; Phair, L.; Wozniak, G. J.; Beaulieu, L.; Breuer, H.; Korteling, R. G.; Kwiatkowski, K.; Lefort, T.; Pienkowski, L.; Ruangma, A.; Viola, V. E.; Yennello, S. J.; Albergo, S.; Bieser, F.; Brady, F. P.; Caccia, Z.; Cebra, D. A.; Chacon, A. D.; Chance, J. L.; Choi, Y.; Costa, S.; Gilkes, M. L.; Hauger, J. A.; Hirsch, A. S.; Hjort, E. L.; Insolia, A.; Justice, M.; Keane, D.; Kintner, J. C.; Lindenstruth, V.; Lisa, M. A.; Matis, H. S.; McMahan, M.; McParland, C.; Müller, W. F. J.; Olson, D. L.; Partlan, M. D.; Porile, N. T.; Potenza, R.; Rai, G.; Rasmussen, J.; Ritter, H. G.; Romanski, J.; Romero, J. L.; Russo, G. V.; Sann, H.; Scharenberg, R. P.; Scott, A.; Shao, Y.; Srivastava, B. K.; Symons, T. J. M.; Tincknell, M.; Tuvé, C.; Wang, S.; Warren, P.; Wieman, H. H.; Wienold, T.; Wolf, K.

    2002-04-01

    The multifragmentation data of the ISiS Collaboration and the EOS Collaboration are examined. Fisher's droplet formalism, modified to account for Coulomb energy, is used to determine the critical exponents τ and σ, the surface energy coefficient c0, the pressure-temperature-density coexistence curve of finite nuclear matter and the location of the critical point. .

  8. New Features of Shape Coexistence in Sm152

    NASA Astrophysics Data System (ADS)

    Garrett, P. E.; Kulp, W. D.; Wood, J. L.; Bandyopadhyay, D.; Choudry, S.; Dashdorj, D.; Lesher, S. R.; McEllistrem, M. T.; Mynk, M.; Orce, J. N.; Yates, S. W.

    2009-08-01

    Excited states in Sm152 have been investigated with the Sm152(n,n'γ) reaction. The lowest four negative-parity band structures have been characterized in detail with respect to their absolute decay properties. Specifically, a new Kπ=0- band has been assigned with its 1- band head at 1681 keV. This newly observed band has a remarkable similarity in its E1 transition rates for decay to the first excited Kπ=0+ band at 684 keV to the lowest Kπ=0- band and its decay to the ground-state band. Based on these decay properties, as well as energy considerations, this new band is assigned as a Kπ=0- octupole excitation based on the Kπ=02+ state. An emerging pattern of repeating excitations built on the 02+ level similar to those built on the ground state may indicate that Sm152 is a complex example of shape coexistence rather than a critical point nucleus.

  9. Shape coexistence in neutron-rich odd-mass S isotopes

    NASA Astrophysics Data System (ADS)

    Mijatovic, Tea; Kobayashi, Nobuyuki; Iwasaki, Hiro; Loelius, Charles; Whitmore, Kenneth; Elder, Robert; Gade, Alexandra; Bazin, Daniel; Weisshaar, Dirk; Bender, Peter; Belarge, Joe; Lunderberg, Eric; Elman, Brandon; Longfellow, Brenden; Dewald, Alfred; Haylett, Thoryn; Mathry, Michael; Heil, Sebastian

    2017-01-01

    Collective motions in atomic nuclei at low excitation energies have been characterized by the ground-state shape as a single basis. This picture can be altered in exotic nuclei with unusual proton-to-neutron ratios if the nuclear shape can change drastically at low spin. Recently, there has been an increasing interest for shape-coexistence phenomena in neutron-rich S isotopes and studies suggested fairly large collectivity in 40 , 42 , 44S isotopes. We will discuss the search for isomeric or long-lived states in 45S for which no excited states are known in the literature and the pursuit to fully characterize the band structure of the low-lying states in 43,45S, which provide key information to establish a comprehensive picture of the shape coexistence in this region. Direct model-independent measurements of the 43,45S excited states were realized by applying the Recoil Distance Method with the TRIPLEX Plunger in conjunction with GRETINA to fast rare isotope beams at the NSCL.

  10. Nuclear shape, mechanics, and mechanotransduction.

    PubMed

    Dahl, Kris Noel; Ribeiro, Alexandre J S; Lammerding, Jan

    2008-06-06

    In eukaryotic cells, the nucleus contains the genome and is the site of transcriptional regulation. The nucleus is the largest and stiffest organelle and is exposed to mechanical forces transmitted through the cytoskeleton from outside the cell and from force generation within the cell. Here, we discuss the effect of intra- and extracellular forces on nuclear shape and structure and how these force-induced changes could be implicated in nuclear mechanotransduction, ie, force-induced changes in cell signaling and gene transcription. We review mechanical studies of the nucleus and nuclear structural proteins, such as lamins. Dramatic changes in nuclear shape, organization, and stiffness are seen in cells where lamin proteins are mutated or absent, as in genetically engineered mice, RNA interference studies, or human disease. We examine the different mechanical pathways from the force-responsive cytoskeleton to the nucleus. We also highlight studies that link changes in nuclear shape with cell function during developmental, physiological, and pathological modifications. Together, these studies suggest that the nucleus itself may play an important role in the response of the cell to force.

  11. New Features of Shape Coexistence in {sup 152}Sm

    SciTech Connect

    Garrett, P. E.; Kulp, W. D.; Wood, J. L.; Bandyopadhyay, D.; Choudry, S.; Lesher, S. R.; McEllistrem, M. T.; Mynk, M.; Orce, J. N.; Yates, S. W.; Dashdorj, D.

    2009-08-07

    Excited states in {sup 152}Sm have been investigated with the {sup 152}Sm(n,n{sup '}gamma) reaction. The lowest four negative-parity band structures have been characterized in detail with respect to their absolute decay properties. Specifically, a new K{sup p}i=0{sup -} band has been assigned with its 1{sup -} band head at 1681 keV. This newly observed band has a remarkable similarity in its E1 transition rates for decay to the first excited K{sup p}i=0{sup +} band at 684 keV to the lowest K{sup p}i=0{sup -} band and its decay to the ground-state band. Based on these decay properties, as well as energy considerations, this new band is assigned as a K{sup p}i=0{sup -} octupole excitation based on the K{sup p}i=0{sub 2}{sup +} state. An emerging pattern of repeating excitations built on the 0{sub 2}{sup +} level similar to those built on the ground state may indicate that {sup 152}Sm is a complex example of shape coexistence rather than a critical point nucleus.

  12. Shape coexistence at low spin in the Z = 50 region and its spectroscopic signatures

    NASA Astrophysics Data System (ADS)

    Garrett, P. E.

    2016-08-01

    Nuclei in the Z = 50 region provide excellent examples of shape coexistence, the establishment of which occurred through the use of detailed spectroscopy, based not only on γ-ray spectroscopy but also conversion electron, particle transfer, Coulomb excitation, and lifetime measurements. The evidence to date strongly suggests that the presence of coexisting shapes arises from the promotion of protons across the Z = 50 closed shell and the strong correlations arising from interplay of the pairing and quadrupole interactions. The evidence for the presence of shape coexistence in the Z = 50 region, at low spin and low excitation energies, will be presented and clues for the microscopic origin explored.

  13. A microscopic study on shape transition and shape coexistence in superdeformed nuclei

    SciTech Connect

    Kanthimathi, G.; Boomadevi, N.; Rajasekaran, T. R.

    2012-08-15

    Superdeformed nuclei at high-spin states in several mass regions are investigated within a microscopic approach using cranked Nilsson-Strutinsky formalism to explore the equilibrium deformations in the ground state and their evolution with spin. Shape transition from normal deformed to superdeformed states with increasing spin is studied and a clear picture of shape coexistence is provided. Detailed information on spin, rotational energy, dynamical moment of inertia, and rotational frequency of superdeformed rotational bands is presented and the general features of superdeformed bands in certain mass regions are outlined. Rotational energy and dynamical moment of inertia are compared with available experimental data and the impact of temperature and pairing on superdeformed configuration are discussed.

  14. Cell Shape Dependent Regulation of Nuclear Morphology

    PubMed Central

    Chen, Bo; Co, Carlos; Ho, Chia-Chi

    2015-01-01

    Recent studies suggest that actin filaments are essential in how a cell controls its nuclear shape. However, little is known about the relative importance of membrane tension in determining nuclear morphology. In this study, we used adhesive micropatterned substrates to alter the cellular geometry (aspect ratio, size, and shape) that allowed direct membrane tension or without membrane lateral contact with the nucleus and investigate nuclear shape remodeling and orientation on a series of rectangular shapes. Here we showed that at low cell aspect ratios the orientation of the nucleus was regulated by actin filaments while cells with high aspect ratios can maintain nuclear shape and orientation even when actin polymerization was blocked. A model adenocarcinoma cell showed similar behavior in the regulation of nuclear shape in response to changes in cell shape but actin filaments were essential in maintaining cell shape. Our results highlight the two distinct mechanisms to regulate nuclear shape through cell shape control and the difference between fibroblasts and a model cancerous cell in cell adhesion and cell shape control. PMID:26210179

  15. Cell shape dependent regulation of nuclear morphology.

    PubMed

    Chen, Bo; Co, Carlos; Ho, Chia-Chi

    2015-10-01

    Recent studies suggest that actin filaments are essential in how a cell controls its nuclear shape. However, little is known about the relative importance of membrane tension in determining nuclear morphology. In this study, we used adhesive micropatterned substrates to alter the cellular geometry (aspect ratio, size, and shape) that allowed direct membrane tension or without membrane lateral contact with the nucleus and investigate nuclear shape remodeling and orientation on a series of rectangular shapes. Here we showed that at low cell aspect ratios the orientation of the nucleus was regulated by actin filaments while cells with high aspect ratios can maintain nuclear shape and orientation even when actin polymerization was blocked. A model adenocarcinoma cell showed similar behavior in the regulation of nuclear shape in response to changes in cell shape but actin filaments were essential in maintaining cell shape. Our results highlight the two distinct mechanisms to regulate nuclear shape through cell shape control and the difference between fibroblasts and a model cancerous cell in cell adhesion and cell shape control. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Lifetime measurements probing triple shape coexistence in 175Au

    NASA Astrophysics Data System (ADS)

    Watkins, H.; Joss, D. T.; Grahn, T.; Page, R. D.; Carroll, R. J.; Dewald, A.; Greenlees, P. T.; Hackstein, M.; Herzberg, R.-D.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Kröll, T.; Krücken, R.; Labiche, M.; Leino, M.; Lumley, N.; Maierbeck, P.; Nyman, M.; Nieminen, P.; O'Donnell, D.; Ollier, J.; Pakarinen, J.; Peura, P.; Pissulla, T.; Rahkila, P.; Revill, J. P.; Rother, W.; Ruotsalainen, P.; Rigby, S. V.; Sarén, J.; Sapple, P. J.; Scheck, M.; Scholey, C.; Simpson, J.; Sorri, J.; Uusitalo, J.; Venhart, M.

    2011-11-01

    Lifetimes of the low-lying excited states in the very neutron-deficient nucleus 175Au have been measured by the recoil-distance Doppler-shift method using γ-ray spectra obtained with the recoil-decay tagging technique. Transition quadrupole moments and reduced transition probabilities extracted for this odd-Z nucleus indicate the existence of three different shapes and the competition between collective and noncollective structures.

  17. Energy density functional analysis of shape coexistence in {sup 44}S

    SciTech Connect

    Li, Z. P.; Yao, J. M.; Vretenar, D.; Niksic, T.; Meng, J.

    2012-10-20

    The structure of low-energy collective states in the neutron-rich nucleus {sup 44}S is analyzed using a microscopic collective Hamiltonian model based on energy density functionals (EDFs). The calculated triaxial energy map, low-energy spectrum and corresponding probability distributions indicate a coexistence of prolate and oblate shapes in this nucleus.

  18. Shape coexistence in the neutron-deficient Pt isotopes in a configuration mixing IBM

    SciTech Connect

    Morales, Irving O.; Vargas, Carlos E.; Frank, Alejandro

    2004-09-13

    The recently proposed matrix-coherent state approach for configuration mixing IBM is used to describe the evolving geometry of the neutron deficient Pt isotopes. It is found that the Potential Energy Surface (PES) of the Platinum isotopes evolves, when the number of neutrons decreases, from spherical to oblate and then to prolate shapes, in agreement with experimental measurements. Oblate-Prolate shape coexistence is observed in 194,192Pt isotopes.

  19. Multi-quasiparticle excitation: Extending shape coexistence in A~190 neutron-deficient nuclei

    NASA Astrophysics Data System (ADS)

    Shi, Yue; Xu, F. R.; Liu, H. L.; Walker, P. M.

    2010-10-01

    Multi-quasiparticle high-K states in neutron-deficient mercury, lead, and polonium isotopes have been investigated systematically by means of configuration-constrained potential-energy-surface calculations. An abundance of high-K states is predicted with both prolate and oblate shapes, which extends the shape coexistence of the mass region. Well-deformed shapes provide good conditions for the formation of isomers, as exemplified in Pb188. Of particular interest is the prediction of low-lying 10- states in polonium isotopes, which indicate long-lived isomers.

  20. Multi-quasiparticle excitation: Extending shape coexistence in A{approx}190 neutron-deficient nuclei

    SciTech Connect

    Shi Yue; Liu, H. L.; Xu, F. R.; Walker, P. M.

    2010-10-15

    Multi-quasiparticle high-K states in neutron-deficient mercury, lead, and polonium isotopes have been investigated systematically by means of configuration-constrained potential-energy-surface calculations. An abundance of high-K states is predicted with both prolate and oblate shapes, which extends the shape coexistence of the mass region. Well-deformed shapes provide good conditions for the formation of isomers, as exemplified in {sup 188}Pb. Of particular interest is the prediction of low-lying 10{sup -} states in polonium isotopes, which indicate long-lived isomers.

  1. Nuclear Coexistence: Rethinking U.S. Policy to Promote Stability in an Era of Proliferation

    DTIC Science & Technology

    1994-04-01

    the case of nuclear power reactors, most of the costs - for reprocessing facilities, test complexes, bomb fabrication sites, among others - are sunk...1991), for a description of Israel’s development of nuclear weapons. 11. See J.W. de Villiers, Roger Jardine , and Mitchell Reiss, "Why South Africa Gave...South African Gov- ernment, see J.W. de Villiers, Roger Jardine , and Mitchell Reiss, "Why South 44 ... Nuclear Coexistence Africa Gave Up the Bomb

  2. Shape coexistence in 67Co, 66,68,70,72Ni, and 71Cu

    NASA Astrophysics Data System (ADS)

    Walters, W. B.; Chiara, C. J.; Janssens, R. V. F.; Weisshaar, D.; Otsuka, T.; Tsunoda, Y.; Recchia, F.; Gade, A.; Harker, J. L.; Albers, M.; Alcorta, M.; Bader, V. M.; Baugher, T.; Bazin, D.; Berryman, J. S.; Bertone, P. F.; Campbell, C. M.; Carpenter, M. P.; Chen, J.; Crawford, H. L.; David, H. M.; Doherty, D. T.; Hoffman, C. R.; Honma, M.; Kondev, F. G.; Korichi, A.; Langer, C.; Larson, N.; Lauritsen, T.; Liddick, S. N.; Lunderberg, E.; Macchiavelli, A. O.; Noji, S.; Prokop, C.; Rogers, A. M.; Seweryniak, D.; Shimizu, N.; Stroberg, S. R.; Suchyta, S.; Utsuno, Y.; Williams, S. J.; Wimmer, K.; Zhu, S.

    2015-10-01

    Analyses of data from both deep inelastic reactions at Argonne National Laboratory and single- and multiple-particle knockout reactions at Michigan State University revealed new γ-ray transitions in even-even 66,68,70,72Ni38,40,42,44 and in 67Co40 that provide strong evidence for multiple shape coexistence at N = 38 and 40 and deep prolate minima in 70Ni42 and isotonic 71Cu42. A new transition at 642 keV is proposed for 66Ni as the prolate 2+ to 0+ transition. Two new transitions in 72Ni at 915 and 1225 keV were identified in the knock-out reaction study and could represent de-population of prolate states. Taken together with recent theoretical work using the Monte Carlo shell model, a well defined region of shape coexistence can be seen existing precisely between 38 ≤ N ≤44 for Co, Ni, and Cu nuclei.

  3. Coexistence of specialist and generalist species is shaped by dispersal and environmental factors.

    PubMed

    Büchi, Lucie; Vuilleumier, Séverine

    2014-05-01

    Disentangling the mechanisms mediating the coexistence of habitat specialists and generalists has been a long-standing subject of investigation. However, the roles of species traits and environmental and spatial factors have not been assessed in a unifying theoretical framework. Theory suggests that specialist species are more competitive in natural communities. However, empirical work has shown that specialist species are declining worldwide due to habitat loss and fragmentation. We addressed the question of the coexistence of specialist and generalist species with a spatially explicit metacommunity model in continuous and heterogeneous environments. We characterized how species' dispersal abilities, the number of interacting species, environmental spatial autocorrelation, and disturbance impact community composition. Our results demonstrated that species' dispersal ability and the number of interacting species had a drastic influence on the composition of metacommunities. More specialized species coexisted when species had large dispersal abilities and when the number of interacting species was high. Disturbance selected against highly specialized species, whereas environmental spatial autocorrelation had a marginal impact. Interestingly, species richness and niche breadth were mainly positively correlated at the community scale but were negatively correlated at the metacommunity scale. Numerous diversely specialized species can thus coexist, but both species' intrinsic traits and environmental factors interact to shape the specialization signatures of communities at both the local and global scales.

  4. Beyond-mean-field study of the hyperon impurity effect in hypernuclei with shape coexistence

    NASA Astrophysics Data System (ADS)

    Wu, X. Y.; Mei, H.; Yao, J. M.; Zhou, Xian-Rong

    2017-03-01

    Background: The hyperon impurity effect in nuclei has been extensively studied in different mean-field models. Recently, there is a controversy about whether the Λ hyperon is more tightly bound in the normal deformed (ND) states than that in the superdeformed (SD) states. Purpose: This article is aimed to provide a beyond-mean-field study of the low-lying states of hypernuclei with shape coexistence and to shed some light on the controversy. Method: The models of relativistic mean field and beyond based on a relativistic point-coupling energy functional are adopted to study the low-lying states of both Ar37Lambda; and 36Ar. The wave functions of low-lying states are constructed as a superposition of a set of relativistic mean-field states with different values of quadrupole deformation parameter. The projections onto both particle number and angular momentum are considered. Results: The Λ binding energies in both ND and SD states of Ar37Lambda; are studied in the case of the Λ hyperon occupying the s ,p , or d state in the spherical limit, respectively. For comparison, four sets of nucleon-hyperon point-coupling interactions are used, respectively. Moreover, the spectra of low-lying states in 36Ar and Ar Lambda;s37 are calculated based on the same nuclear energy density functional. The results indicate that the SD states exist in Ar37Lambda; for all four effective interactions. Furthermore, the Λs reduces the quadrupole collectivity of ND states to a greater extent than that of SD states. For Ar37Lambda;, the beyond-mean field decreases the Λs binding energy of the SD state by 0.17 MeV, but it almost has no effect on that of the ND state. Conclusions: In Ar Lambda;s37 , the Λp and Λd binding energies of the SD states are always larger than those of the ND states. For Λs, the conclusion depends on the effective nucleon-hyperon interaction. Moreover, the beyond-mean-field model

  5. New low-energy 0+ state and shape coexistence in 70Ni

    NASA Astrophysics Data System (ADS)

    Prokop, C. J.; Crider, B. P.; Liddick, S. N.; Ayangeakaa, A. D.; Carpenter, M. P.; Carroll, J. J.; Chen, J.; Chiara, C. J.; David, H. M.; Dombos, A. C.; Go, S.; Harker, J.; Janssens, R. V. F.; Larson, N.; Lauritsen, T.; Lewis, R.; Quinn, S. J.; Recchia, F.; Seweryniak, D.; Spyrou, A.; Suchyta, S.; Walters, W. B.; Zhu, S.

    2015-12-01

    In recent models, the neutron-rich Ni isotopes around N =40 are predicted to exhibit multiple low-energy excited 0+ states attributed to neutron and proton excitations across both the N =40 and Z =28 shell gaps. In 68Ni, the three observed 0+ states have been interpreted in terms of triple shape coexistence between spherical, oblate, and prolate deformed shapes. In the present work a new (02+) state at an energy of 1567 keV has been discovered in 70Ni by using β -delayed, γ -ray spectroscopy following the decay of 70Co. The precipitous drop in the energy of the prolate-deformed 0+ level between 68Ni and 70Ni with the addition of two neutrons compares favorably with results of Monte Carlo shell-model calculations carried out in the large f p g9 /2d5 /2 model space, which predict a 02+ state at 1525 keV in 70Ni. The result extends the shape-coexistence picture in the region to 70Ni and confirms the importance of the role of the tensor component of the monopole interaction in describing the structure of neutron-rich nuclei.

  6. Shape coexistence in neutron-rich strontium isotopes at N = 60

    NASA Astrophysics Data System (ADS)

    Clément, E.; Zielińska, M.

    2017-08-01

    The structure of neutron-rich {}{96,98}Sr nuclei was investigated by low-energy Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. The results support the scenario of a shape transition at N = 60, giving rise to the coexistence of a highly deformed prolate and a spherical configuration in 98Sr with low configuration mixing. They are discussed in the context of systematics of quadrupole moments and transition probabilities in the N = 60 region.

  7. Shape coexistence and the role of axial asymmetry in 72Ge

    NASA Astrophysics Data System (ADS)

    Ayangeakaa, A. D.; Janssens, R. V. F.; Wu, C. Y.; Allmond, J. M.; Wood, J. L.; Zhu, S.; Albers, M.; Almaraz-Calderon, S.; Bucher, B.; Carpenter, M. P.; Chiara, C. J.; Cline, D.; Crawford, H. L.; David, H. M.; Harker, J.; Hayes, A. B.; Hoffman, C. R.; Kay, B. P.; Kolos, K.; Korichi, A.; Lauritsen, T.; Macchiavelli, A. O.; Richard, A.; Seweryniak, D.; Wiens, A.

    2016-03-01

    The quadrupole collectivity of low-lying states and the anomalous behavior of the 02+ and 23+ levels in 72Ge are investigated via projectile multi-step Coulomb excitation with GRETINA and CHICO-2. A total of forty six E2 and M1 matrix elements connecting fourteen low-lying levels were determined using the least-squares search code, GOSIA. Evidence for triaxiality and shape coexistence, based on the model-independent shape invariants deduced from the Kumar-Cline sum rule, is presented. These are interpreted using a simple two-state mixing model as well as multi-state mixing calculations carried out within the framework of the triaxial rotor model. The results represent a significant milestone towards the understanding of the unusual structure of this nucleus.

  8. Shape-coexisting rotation in neutron-deficient Hg and Pb nuclei

    NASA Astrophysics Data System (ADS)

    Jiao, C. F.; Shi, Yue; Liu, H. L.; Xu, F. R.; Walker, P. M.

    2015-03-01

    For a shape-soft nucleus, the deformation change with increasing angular momentum of rotation can be significant. Total-Routhian-surface (TRS) calculations include the shape changes, but angular momentum is not conserved (neither is it a good quantum number, nor is it kept unchanged in the whole TRS mesh). In the projected shell model (PSM), the angular momentum appears as a good quantum number, but calculations have usually been performed with fixed deformation. In the present work, by performing angular-momentum projection on the mean-field potential-energy surface (PES), we can obtain an angular-momentum-conserved PES which gives deformation for a rotational state at a given spin. In order to investigate the shape-changing effect, we have chosen neutron-deficient Hg and Pb isotopes in which shape coexistence occurs. We interpret the irregular rotational behavior of the oblate bands at low spin as arising from deformation changes which are induced by collective rotation. At higher spin, the oblate rotational spectrum can also be influenced by the crossing between the K =0 ground-state band and a low-K two-quasineutron band. Calculated g factors for the states of oblate bands are given for future experimental testing, and the intrinsic structures of high-K oblate states are investigated.

  9. Shapes and stability of algebraic nuclear models

    NASA Technical Reports Server (NTRS)

    Lopez-Moreno, Enrique; Castanos, Octavio

    1995-01-01

    A generalization of the procedure to study shapes and stability of algebraic nuclear models introduced by Gilmore is presented. One calculates the expectation value of the Hamiltonian with respect to the coherent states of the algebraic structure of the system. Then equilibrium configurations of the resulting energy surface, which depends in general on state variables and a set of parameters, are classified through the Catastrophe theory. For one- and two-body interactions in the Hamiltonian of the interacting Boson model-1, the critical points are organized through the Cusp catastrophe. As an example, we apply this Separatrix to describe the energy surfaces associated to the Rutenium and Samarium isotopes.

  10. Prolate-Spherical Shape Coexistence at N=28 in {sup 44}S

    SciTech Connect

    Force, C.; Grevy, S.; Sorlin, O.; Caceres, L.; De Oliveira, F.; Saint-Laurent, M. G.; Stefan, I.; Stodel, C.; Rotaru, F.; Borcea, R.; Buta, A.; Negoita, F.; Stanoiu, M.; Mrazek, J.; Dlouhy, Z.; Achouri, N. L.; Angelique, J. C.; Bastin, B.

    2010-09-03

    The structure of {sup 44}S has been studied by using delayed {gamma} and electron spectroscopy. The decay rates of the 0{sub 2}{sup +} isomeric state to the 2{sub 1}{sup +} and 0{sub 1}{sup +} states, measured for the first time, lead to a reduced transition probability B(E2: 2{sub 1}{sup +}{yields}0{sub 2}{sup +})=8.4(26) e{sup 2} fm{sup 4} and a monopole strength {rho}{sup 2}(E0: 0{sub 2}{sup +}{yields}0{sub 1}{sup +})=8.7(7)x10{sup -3}. Comparisons to shell model calculations point towards prolate-spherical shape coexistence, and a two-level mixing model is used to extract a weak mixing between the two configurations.

  11. Prolate-spherical shape coexistence at N=28 in 44S.

    PubMed

    Force, C; Grévy, S; Gaudefroy, L; Sorlin, O; Cáceres, L; Rotaru, F; Mrazek, J; Achouri, N L; Angélique, J C; Azaiez, F; Bastin, B; Borcea, R; Buta, A; Daugas, J M; Dlouhy, Z; Dombrádi, Zs; De Oliveira, F; Negoita, F; Penionzhkevich, Y; Saint-Laurent, M G; Sohler, D; Stanoiu, M; Stefan, I; Stodel, C; Nowacki, F

    2010-09-03

    The structure of 44S has been studied by using delayed γ and electron spectroscopy. The decay rates of the 02+ isomeric state to the 2(1)+ and 0(1)+ states, measured for the first time, lead to a reduced transition probability B(E2: 2(1)+→0(2)+)=8.4(26) e(2) fm4 and a monopole strength ρ2(E0: 0(2)+→0(1)+)=8.7(7)×10(-3). Comparisons to shell model calculations point towards prolate-spherical shape coexistence, and a two-level mixing model is used to extract a weak mixing between the two configurations.

  12. Shape coexistence effects on stellar weak interaction rates of proton-rich nuclei within beyond-mean-field approach

    NASA Astrophysics Data System (ADS)

    Petrovici, A.; Andrei, O.

    2017-06-01

    Relevant for the astrophysical rp-process, proton-rich A˜70 nuclei manifesting shape coexistence have been investigated in the frame of the beyond-mean-field complex Excited Vampir variational model with symmetry projection before variation using the effective interaction obtained from a G-matrix based on BonnA/BonnCD potential. Reliable predictions on stellar weak interaction rates emerged starting from the realistic description of the experimentally accesible properties. The influence of shape coexistence and mixing in the structure of the low-lying parent states as well as in the independently calculated daughter states on weak interaction rates under X-ray burst environment is discussed.

  13. Recent advances in understanding nuclear size and shape.

    PubMed

    Mukherjee, Richik N; Chen, Pan; Levy, Daniel L

    2016-04-25

    Size and shape are important aspects of nuclear structure. While normal cells maintain nuclear size within a defined range, altered nuclear size and shape are associated with a variety of diseases. It is unknown if altered nuclear morphology contributes to pathology, and answering this question requires a better understanding of the mechanisms that control nuclear size and shape. In this review, we discuss recent advances in our understanding of the mechanisms that regulate nuclear morphology, focusing on nucleocytoplasmic transport, nuclear lamins, the endoplasmic reticulum, the cell cycle, and potential links between nuclear size and size regulation of other organelles. We then discuss the functional significance of nuclear morphology in the context of early embryonic development. Looking toward the future, we review new experimental approaches that promise to provide new insights into mechanisms of nuclear size control, in particular microfluidic-based technologies, and discuss how altered nuclear morphology might impact chromatin organization and physiology of diseased cells.

  14. Recent advances in understanding nuclear size and shape

    PubMed Central

    Mukherjee, Richik N.; Chen, Pan; Levy, Daniel L.

    2016-01-01

    ABSTRACT Size and shape are important aspects of nuclear structure. While normal cells maintain nuclear size within a defined range, altered nuclear size and shape are associated with a variety of diseases. It is unknown if altered nuclear morphology contributes to pathology, and answering this question requires a better understanding of the mechanisms that control nuclear size and shape. In this review, we discuss recent advances in our understanding of the mechanisms that regulate nuclear morphology, focusing on nucleocytoplasmic transport, nuclear lamins, the endoplasmic reticulum, the cell cycle, and potential links between nuclear size and size regulation of other organelles. We then discuss the functional significance of nuclear morphology in the context of early embryonic development. Looking toward the future, we review new experimental approaches that promise to provide new insights into mechanisms of nuclear size control, in particular microfluidic-based technologies, and discuss how altered nuclear morphology might impact chromatin organization and physiology of diseased cells. PMID:26963026

  15. Joint modeling of cell and nuclear shape variation

    PubMed Central

    Johnson, Gregory R.; Buck, Taraz E.; Sullivan, Devin P.; Rohde, Gustavo K.; Murphy, Robert F.

    2015-01-01

    Modeling cell shape variation is critical to our understanding of cell biology. Previous work has demonstrated the utility of nonrigid image registration methods for the construction of nonparametric nuclear shape models in which pairwise deformation distances are measured between all shapes and are embedded into a low-dimensional shape space. Using these methods, we explore the relationship between cell shape and nuclear shape. We find that these are frequently dependent on each other and use this as the motivation for the development of combined cell and nuclear shape space models, extending nonparametric cell representations to multiple-component three-dimensional cellular shapes and identifying modes of joint shape variation. We learn a first-order dynamics model to predict cell and nuclear shapes, given shapes at a previous time point. We use this to determine the effects of endogenous protein tags or drugs on the shape dynamics of cell lines and show that tagged C1QBP reduces the correlation between cell and nuclear shape. To reduce the computational cost of learning these models, we demonstrate the ability to reconstruct shape spaces using a fraction of computed pairwise distances. The open-source tools provide a powerful basis for future studies of the molecular basis of cell organization. PMID:26354424

  16. Shape Coexistence in 78Ni as the Portal to the Fifth Island of Inversion

    NASA Astrophysics Data System (ADS)

    Nowacki, F.; Poves, A.; Caurier, E.; Bounthong, B.

    2016-12-01

    Large-scale shell-model calculations predict that the region of deformation which comprises the heaviest chromium and iron isotopes at and beyond N =40 will merge with a new one at N =50 in an astonishing parallel to the N =20 and N =28 case in the neon and magnesium isotopes. We propose a valence space including the full p f shell for the protons and the full s d g shell for the neutrons, which represents a comeback of the the harmonic oscillator shells in the very neutron- rich regime. The onset of deformation is understood in the framework of the algebraic SU(3)-like structures linked to quadrupole dominance. Our calculations preserve the doubly magic nature of the ground state of 78Ni, which, however, exhibits a well-deformed prolate band at low excitation energy, providing a striking example of shape coexistence far from stability. This new IOI adds to the four well-documented ones at N =8 , 20, 28, and 40.

  17. Possible shape coexistence and magnetic dipole transitions in {sup 17}C and {sup 21}Ne

    SciTech Connect

    Sagawa, H.; Zhou, X. R.; Suzuki, Toshio; Yoshida, N.

    2008-10-15

    Magnetic dipole (M1) transitions of N=11 nuclei {sup 17}C and {sup 21}Ne are investigated by using shell model and deformed Skyrme Hartree-Fock + blocked BCS wave functions. Shell model calculations predict well observed energy spectra and magnetic dipole transitions in {sup 21}Ne, while the results are rather poor to predict these observables in {sup 17}C. In the deformed HF calculations, the ground states of the two nuclei are shown to have large prolate deformations close to {beta}{sub 2}=0.4. It is also pointed out that the first K{sup {pi}}=1/2{sup +} state in {sup 21}Ne is prolately deformed, while the first K{sup {pi}}=1/2{sup +} state in {sup 17}C is predicted to have a large oblate deformation close to the ground state in energy, We point out that the experimentally observed large hindrance of the M1 transition between I{sup {pi}}=1/2{sup +} and 3/2{sup +} in {sup 17}C can be attributed to a shape coexistence near the ground state of {sup 17}C.

  18. Shape Coexistence, Triaxiality, Chiral Bands in Neutron-Rich Nuclei and Hot Fission Mode

    NASA Astrophysics Data System (ADS)

    Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Zhu, S. J.; Luo, Y. X.; Rasmussen, J. O.; Gore, P. M.; Jones, E. F.; Fong, D.; Li, K.; Beyer, C. J.; Chaturvedi, L.; Xu, R. Q.; Yang, L. M.; Jiang, Z.; Zhang, Z.; Xiou, S. D.; Zhang, X. Q.; Ter-Akopian, G. M.; Daniel, A. V.; Oganessian, Yu.; Dimitrov, V.; Frauendorf, S.; Gelberg, A.; Kormicki, J.; Gilat, J.; Lee, I. Y.; Fallon, P.; Cole, J. D.; Drigert, M. W.; Stoyer, M. A.; Ginter, T. N.; Wu, S. C.; Donangelo, R.

    2005-09-01

    The structure of neutron-rich nuclei in the A=100 region have been investigated via prompt γ-γ-γ coincidences in the spontaneous fission of 252Cf at Gammasphere. New levels are observed in 93,95,97Sr, 99,101Y, 101,105Nb, 104,106Mo, 105,107,109Tc, 111,113Rh and 115,117Ag. The level structures show a clear evolution from spherical single particle structures seen in Sr, to symmetric, large prolate deformation in Y, to increasing triaxial shapes with increasing Z in Nb, Mo, Tc, Rh and Ag. Rigid triaxial-plus-rotor calculations were carried out for 107Tc and 111,113Rh. Best fits in 107Tc and 111,113Rb are for prolate β2 ~ 0.3 and γ increasing from -22.5° in 107Tc to near maximum triaxiality, γ = -28° in 111,113Rh. A K= 1/2 intruder band with symmetric deformation is found to coexist with the triaxial asymmetric bands in the Tc and Rh nuclei. In 106Mo, two sets of ΔI=1 bands have all the characteristics of chiral doublets. Tilted axis cranking calculations support the chiral assignment and indicate these form a new type of chiral band with a one and two phonon chiral vibrational nature associated essentially with the neutrons. These new type chiral doublets demonstrate the general nature of chirality in nuclei. Binary yields of Mo-Ba and Ru-Xe were determined with higher accuracy. The hot fission mode is seen only in Mo-Ba where it goes via a type of hyperdeformed shape for 144,145,146Ba with a 4.7% intensity.

  19. Moving Cell Boundaries Drive Nuclear Shaping during Cell Spreading

    PubMed Central

    Li, Yuan; Lovett, David; Zhang, Qiao; Neelam, Srujana; Kuchibhotla, Ram Anirudh; Zhu, Ruijun; Gundersen, Gregg G.; Lele, Tanmay P.; Dickinson, Richard B.

    2015-01-01

    The nucleus has a smooth, regular appearance in normal cells, and its shape is greatly altered in human pathologies. Yet, how the cell establishes nuclear shape is not well understood. We imaged the dynamics of nuclear shaping in NIH3T3 fibroblasts. Nuclei translated toward the substratum and began flattening during the early stages of cell spreading. Initially, nuclear height and width correlated with the degree of cell spreading, but over time, reached steady-state values even as the cell continued to spread. Actomyosin activity, actomyosin bundles, microtubules, and intermediate filaments, as well as the LINC complex, were all dispensable for nuclear flattening as long as the cell could spread. Inhibition of actin polymerization as well as myosin light chain kinase with the drug ML7 limited both the initial spreading of cells and flattening of nuclei, and for well-spread cells, inhibition of myosin-II ATPase with the drug blebbistatin decreased cell spreading with associated nuclear rounding. Together, these results show that cell spreading is necessary and sufficient to drive nuclear flattening under a wide range of conditions, including in the presence or absence of myosin activity. To explain this observation, we propose a computational model for nuclear and cell mechanics that shows how frictional transmission of stress from the moving cell boundaries to the nuclear surface shapes the nucleus during early cell spreading. Our results point to a surprisingly simple mechanical system in cells for establishing nuclear shapes. PMID:26287620

  20. Moving Cell Boundaries Drive Nuclear Shaping during Cell Spreading.

    PubMed

    Li, Yuan; Lovett, David; Zhang, Qiao; Neelam, Srujana; Kuchibhotla, Ram Anirudh; Zhu, Ruijun; Gundersen, Gregg G; Lele, Tanmay P; Dickinson, Richard B

    2015-08-18

    The nucleus has a smooth, regular appearance in normal cells, and its shape is greatly altered in human pathologies. Yet, how the cell establishes nuclear shape is not well understood. We imaged the dynamics of nuclear shaping in NIH3T3 fibroblasts. Nuclei translated toward the substratum and began flattening during the early stages of cell spreading. Initially, nuclear height and width correlated with the degree of cell spreading, but over time, reached steady-state values even as the cell continued to spread. Actomyosin activity, actomyosin bundles, microtubules, and intermediate filaments, as well as the LINC complex, were all dispensable for nuclear flattening as long as the cell could spread. Inhibition of actin polymerization as well as myosin light chain kinase with the drug ML7 limited both the initial spreading of cells and flattening of nuclei, and for well-spread cells, inhibition of myosin-II ATPase with the drug blebbistatin decreased cell spreading with associated nuclear rounding. Together, these results show that cell spreading is necessary and sufficient to drive nuclear flattening under a wide range of conditions, including in the presence or absence of myosin activity. To explain this observation, we propose a computational model for nuclear and cell mechanics that shows how frictional transmission of stress from the moving cell boundaries to the nuclear surface shapes the nucleus during early cell spreading. Our results point to a surprisingly simple mechanical system in cells for establishing nuclear shapes.

  1. Acquired phototrophy stabilises coexistence and shapes intrinsic dynamics of an intraguild predator and its prey.

    PubMed

    Moeller, Holly V; Peltomaa, Elina; Johnson, Matthew D; Neubert, Michael G

    2016-04-01

    In marine ecosystems, acquired phototrophs - organisms that obtain their photosynthetic ability by hosting endosymbionts or stealing plastids from their prey - are omnipresent. Such taxa function as intraguild predators yet depend on their prey to periodically obtain chloroplasts. We present a new theory for the effects of acquired phototrophy on community dynamics by analysing a mathematical model of this predator-prey interaction and experimentally verifying its predictions with a laboratory model system. We show that acquired phototrophy stabilises coexistence, but that the nature of this coexistence exhibits a 'paradox of enrichment': as light increases, the coexistence between the acquired phototroph and its prey transitions from a stable equilibrium to boom-bust cycles whose amplitude increases with light availability. In contrast, heterotrophs and mixotrophic acquired phototrophs (that obtain < 30% of their carbon from photosynthesis) do not exhibit such cycles. This prediction matches field observations, in which only strict ( > 95% of carbon from photosynthesis) acquired phototrophs form blooms.

  2. The relationship between species richness and ecosystem variability is shaped by the mechanism of coexistence.

    PubMed

    Tredennick, Andrew T; Adler, Peter B; Adler, Frederick R

    2017-08-01

    Theory relating species richness to ecosystem variability typically ignores the potential for environmental variability to promote species coexistence. Failure to account for fluctuation-dependent coexistence may explain deviations from the expected negative diversity-ecosystem variability relationship, and limits our ability to predict the consequences of increases in environmental variability. We use a consumer-resource model to explore how coexistence via the temporal storage effect and relative nonlinearity affects ecosystem variability. We show that a positive, rather than negative, diversity-ecosystem variability relationship is possible when ecosystem function is sampled across a natural gradient in environmental variability and diversity. We also show how fluctuation-dependent coexistence can buffer ecosystem functioning against increasing environmental variability by promoting species richness and portfolio effects. Our work provides a general explanation for variation in observed diversity-ecosystem variability relationships and highlights the importance of conserving regional species pools to help buffer ecosystems against predicted increases in environmental variability. © 2017 John Wiley & Sons Ltd/CNRS.

  3. Nuclear Calcium Buffering Capacity Shapes Neuronal Architecture*

    PubMed Central

    Mauceri, Daniela; Hagenston, Anna M.; Schramm, Kathrin; Weiss, Ursula; Bading, Hilmar

    2015-01-01

    Calcium-binding proteins (CaBPs) such as parvalbumin are part of the cellular calcium buffering system that determines intracellular calcium diffusion and influences the spatiotemporal dynamics of calcium signals. In neurons, CaBPs are primarily localized to the cytosol and function, for example, in nerve terminals in short-term synaptic plasticity. However, CaBPs are also expressed in the cell nucleus, suggesting that they modulate nuclear calcium signals, which are key regulators of neuronal gene expression. Here we show that the calcium buffering capacity of the cell nucleus in mouse hippocampal neurons regulates neuronal architecture by modulating the expression levels of VEGFD and the complement factor C1q-c, two nuclear calcium-regulated genes that control dendrite geometry and spine density, respectively. Increasing the levels of nuclear calcium buffers by means of expression of a nuclearly targeted form of parvalbumin fused to mCherry (PV.NLS-mC) led to a reduction in VEGFD expression and, as a result, to a decrease in total dendritic length and complexity. In contrast, mRNA levels of the synapse pruning factor C1q-c were increased in neurons expressing PV.NLS-mC, causing a reduction in the density and size of dendritic spines. Our results establish a close link between nuclear calcium buffering capacity and the transcription of genes that determine neuronal structure. They suggest that the development of cognitive deficits observed in neurological conditions associated with CaBP deregulation may reflect the loss of necessary structural features of dendrites and spines. PMID:26231212

  4. The relationship of bull fertility to sperm nuclear shape

    USGS Publications Warehouse

    Ostermeier, G.C.; Sargeant, G.A.; Yandell, B.S.; Parrish, J.J.

    2001-01-01

    group had a linear relationship (r .89, P .05) with fertility. To construct a plot of mean sperm shapes, a novel technique to automatically orient and identify the anterior tip of the sperm head was developed. The mean nuclear shape of high-fertility sperm was more elongated and tapered than those of lower fertility. A discriminant function (P .05) was also constructed that separated the 6 bulls into 2 groups based only on the harmonic amplitudes or sperm nuclear shape. The bulls were correctly classified into the 2 fertility groups. A comparison of sperm chromatin structure analysis (SCSA) and harmonic amplitudes found that overall size variance, anterior roundness, and posterior taperedness of sperm nuclei were related to chromatin stability (P .05). Some of the differences observed in sperm nuclear shape between the high- and lower-fertility bulls may be explained by varying levels of chromatin stability. However, sperm nuclear shape appears to contain additional information from chromatin stability alone. In this particular study, with 6 bulls, all with good chromatin quality, sperm nuclear shape was a better predictor of bull fertility.

  5. How direct competition shapes coexistence and vaccine effects in multi-strain pathogen systems.

    PubMed

    Gjini, Erida; Valente, Carina; Sá-Leão, Raquel; Gomes, M Gabriela M

    2016-01-07

    We describe an integrated modeling framework for understanding strain coexistence in polymorphic pathogen systems. Previous studies have debated the utility of neutral formulations and focused on cross-immunity between strains as a major stabilizing mechanism. Here we convey that direct competition for colonization mediates stable coexistence only when competitive abilities amongst pathogen clones satisfy certain pairwise asymmetries. We illustrate our ideas with nested SIS models of single and dual colonization, applied to polymorphic pneumococcal bacteria. By fitting the models to cross-sectional prevalence data from Portugal (before and after the introduction of a seven-valent pneumococcal conjugate vaccine), we are able to not only statistically compare neutral and non-neutral epidemiological formulations, but also estimate vaccine efficacy, transmission and competition parameters simultaneously. Our study highlights that the response of polymorphic pathogen populations to interventions holds crucial information about strain interactions, which can be extracted by suitable nested modeling.

  6. Discovery of the Shape Coexisting 0{sup +} State in {sup 32}Mg by a Two Neutron Transfer Reaction

    SciTech Connect

    Wimmer, K.; Kroell, T.; Kruecken, R.; Bildstein, V.; Gernhaeuser, R.; Bastin, B.; Bree, N.; Diriken, J.; Van Duppen, P.; Huyse, M.; Patronis, N.; Vermaelen, P.; Voulot, D.; Van de Walle, J.; Wenander, F.; Fraile, L. M.; Chapman, R.; Hadinia, B.; Orlandi, R.; Smith, J. F.

    2010-12-17

    The ''island of inversion'' nucleus {sup 32}Mg has been studied by a (t, p) two neutron transfer reaction in inverse kinematics at REX-ISOLDE. The shape coexistent excited 0{sup +} state in {sup 32}Mg has been identified by the characteristic angular distribution of the protons of the {Delta}L=0 transfer. The excitation energy of 1058 keV is much lower than predicted by any theoretical model. The low {gamma}-ray intensity observed for the decay of this 0{sup +} state indicates a lifetime of more than 10 ns. Deduced spectroscopic amplitudes are compared with occupation numbers from shell-model calculations.

  7. Low-density homogeneous symmetric nuclear matter: Disclosing dinucleons in coexisting phases

    NASA Astrophysics Data System (ADS)

    Arellano, Hugo F.; Delaroche, Jean-Paul

    2015-01-01

    The effect of in-medium dinucleon bound states on self-consistent single-particle fields in Brueckner, Bethe and Goldstone theory is investigated in symmetric nuclear matter at zero temperature. To this end, dinucleon bound state occurences in the 1 S 0 and 3 SD 1 channels are explicitly accounted for --within the continuous choice for the auxiliary fields-- while imposing self-consistency in Brueckner-Hartree-Fock approximation calculations. Searches are carried out at Fermi momenta in the range fm-1, using the Argonne bare nucleon-nucleon potential without resorting to the effective-mass approximation. As a result, two distinct solutions meeting the self-consistency requirement are found with overlapping domains in the interval 0.130 fm-1 0.285 fm-1, corresponding to mass densities between and g cm-3. Effective masses as high as three times the nucleon mass are found in the coexistence domain. The emergence of superfluidity in relationship with BCS pairing gap solutions is discussed.

  8. Nuclear hyperdeformation and the Jacobi shape transition

    SciTech Connect

    Schunck, N.; Dudek, J.

    2007-05-15

    The possibility that atomic nuclei possess stable, extremely elongated (hyperdeformed) shapes at very high angular momentum is investigated in the light of the most recent experimental results. The crucial role of the Jacobi shape transitions for the population of hyperdeformed states is discussed and emphasized. State-of-the-art mean-field calculations including the most recent parametrization of the liquid-drop energy together with thermal effects and minimization algorithms allowing the spanning of a large deformation space predict the existence of a region of hyperdeformed nuclei in the mass A{approx}120-130: Te, Cs, Xe, I, and Ba isotopes. In agreement with predictions presented in reviews by J. Dudek, K. Pomorski, N. Schunck, and N. Dubray [Eur. Phys. J. A 20, 15 (2003)] and J. Dudek, N. Schunck, and N. Dubray [Acta Phys Pol. B 36, 975 (2005)], our extended calculations predict that only very short hyperdeformed bands composed of a dozen discrete transitions at the most are to be expected-in contrast to the results known for the superdeformed bands. We stress the importance of the experimental research in terms of multiple-{gamma} correlation analysis that proved to be very efficient for the superdeformation studies and seems very helpful in the even more difficult search for the discrete transitions in hyperdeformed nuclei.

  9. SUN2 Overexpression Deforms Nuclear Shape and Inhibits HIV

    PubMed Central

    Amraoui, Sonia; di Nunzio, Francesca; Kieffer, Camille; Porrot, Françoise; Opp, Silvana; Diaz-Griffero, Felipe; Casartelli, Nicoletta

    2016-01-01

    ABSTRACT In a previous screen of putative interferon-stimulated genes, SUN2 was shown to inhibit HIV-1 infection in an uncharacterized manner. SUN2 is an inner nuclear membrane protein belonging to the linker of nucleoskeleton and cytoskeleton complex. We have analyzed here the role of SUN2 in HIV infection. We report that in contrast to what was initially thought, SUN2 is not induced by type I interferon, and that SUN2 silencing does not modulate HIV infection. However, SUN2 overexpression in cell lines and in primary monocyte-derived dendritic cells inhibits the replication of HIV but not murine leukemia virus or chikungunya virus. We identified HIV-1 and HIV-2 strains that are unaffected by SUN2, suggesting that the effect is specific to particular viral components or cofactors. Intriguingly, SUN2 overexpression induces a multilobular flower-like nuclear shape that does not impact cell viability and is similar to that of cells isolated from patients with HTLV-I-associated adult T-cell leukemia or with progeria. Nuclear shape changes and HIV inhibition both mapped to the nucleoplasmic domain of SUN2 that interacts with the nuclear lamina. This block to HIV replication occurs between reverse transcription and nuclear entry, and passaging experiments selected for a single-amino-acid change in capsid (CA) that leads to resistance to overexpressed SUN2. Furthermore, using chemical inhibition or silencing of cyclophilin A (CypA), as well as CA mutant viruses, we implicated CypA in the SUN2-imposed block to HIV infection. Our results demonstrate that SUN2 overexpression perturbs both nuclear shape and early events of HIV infection. IMPORTANCE Cells encode proteins that interfere with viral replication, a number of which have been identified in overexpression screens. SUN2 is a nuclear membrane protein that was shown to inhibit HIV infection in such a screen, but how it blocked HIV infection was not known. We show that SUN2 overexpression blocks the infection of certain

  10. Shell Erosion and Shape Coexistence in {sub 16}{sup 43}S{sub 27}

    SciTech Connect

    Gaudefroy, L.; Daugas, J. M.; Girod, M.; Rosse, B.; Meot, V.; Morel, P.; Hass, M.; Kumar, V.; Grevy, S.; Stodel, Ch.; Thomas, J. C.; Force, C.; Angelique, J. C.; Simpson, G.; Balabanski, D. L.; Fiori, E.; Georgiev, G.; Lozeva, R. L.; Kameda, D.

    2009-03-06

    We report on the g-factor measurement of the first isomeric state in {sub 16}{sup 43}S{sub 27}[E{sub x}=320.5(5) keV, T{sub 1/2}=415(5) ns, and g=0.317(4)]. The 7/2{sup -} spin-parity of the isomer and the intruder nature of the ground state of the nucleus are experimentally established for the first time, providing direct and unambiguous evidence of the collapse of the N=28 shell closure in neutron-rich nuclei. The shell model, beyond the mean-field and semiempirical calculations, provides a very consistent description of this nucleus showing that a well deformed prolate and quasispherical states coexist at low energy.

  11. Regulation of nuclear shape and size in plants.

    PubMed

    Meier, Iris; Griffis, Anna Hn; Groves, Norman R; Wagner, Alecia

    2016-06-01

    Nuclear shape and size changes have long been used by cytopathologists to diagnose, stage, and prognose cancer. However, the underlying causalities and molecular mechanisms are largely unknown. The current eukaryotic tree of life groups eukaryotes into five supergroups, with all organisms between humans and yeast falling into the supergroup Opisthokonta. The emergence of model organisms with strong molecular genetic methodology in the other supergroups has recently facilitated a broader evolutionary approach to pressing biological questions. Here, we review what is known about the control of nuclear shape and size in the Archaeplastidae, the supergroup containing the higher plants. We discuss common themes as well as differences toward a more generalized model of how eukaryotic organisms regulate nuclear morphology. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Shape coexistence in the neutron-deficient Pt isotopes in the configuration-mixed IBM

    SciTech Connect

    Vargas, Carlos E.; Campuzano, Cuauhtemoc; Morales, Irving O.; Frank, Alejandro; Van Isacker, Piet

    2008-05-12

    The matrix-coherent state approach in the IBM with configuration mixing is used to describe the geometry of neutron-deficient Pt isotopes. Employing a parameter set for all isotopes determined previously, it is found that the lowest minimum goes from spherical to oblate and finally acquires a prolate shape when approaching the mid-shell Pt isotopes.

  13. First Evidence of Shape Coexistence in the ^{78}Ni Region: Intruder 0_{2}^{+} State in ^{80}Ge.

    PubMed

    Gottardo, A; Verney, D; Delafosse, C; Ibrahim, F; Roussière, B; Sotty, C; Roccia, S; Andreoiu, C; Costache, C; Delattre, M-C; Deloncle, I; Etilé, A; Franchoo, S; Gaulard, C; Guillot, J; Lebois, M; MacCormick, M; Marginean, N; Marginean, R; Matea, I; Mihai, C; Mitu, I; Olivier, L; Portail, C; Qi, L; Stan, L; Testov, D; Wilson, J; Yordanov, D T

    2016-05-06

    The N=48 ^{80}Ge nucleus is studied by means of β-delayed electron-conversion spectroscopy at ALTO. The radioactive ^{80}Ga beam is produced through the isotope separation on line photofission technique and collected on a movable tape for the measurement of γ and e^{-} emission following β decay. An electric monopole E0 transition, which points to a 639(1) keV intruder 0_{2}^{+} state, is observed for the first time. This new state is lower than the 2_{1}^{+} level in ^{80}Ge, and provides evidence of shape coexistence close to one of the most neutron-rich doubly magic nuclei discovered so far, ^{78}Ni. This result is compared with theoretical estimates, helping to explain the role of monopole and quadrupole forces in the weakening of the N=50 gap at Z=32. The evolution of intruder 0_{2}^{+} states towards ^{78}Ni is discussed.

  14. Cytoskeletal prestress regulates nuclear shape and stiffness in cardiac myocytes.

    PubMed

    Lee, Hyungsuk; Adams, William J; Alford, Patrick W; McCain, Megan L; Feinberg, Adam W; Sheehy, Sean P; Goss, Josue A; Parker, Kevin Kit

    2015-11-01

    Mechanical stresses on the myocyte nucleus have been associated with several diseases and potentially transduce mechanical stimuli into cellular responses. Although a number of physical links between the nuclear envelope and cytoplasmic filaments have been identified, previous studies have focused on the mechanical properties of individual components of the nucleus, such as the nuclear envelope and lamin network. The mechanical interaction between the cytoskeleton and chromatin on nuclear deformability remains elusive. Here, we investigated how cytoskeletal and chromatin structures influence nuclear mechanics in cardiac myocytes. Rapid decondensation of chromatin and rupture of the nuclear membrane caused a sudden expansion of DNA, a consequence of prestress exerted on the nucleus. To characterize the prestress exerted on the nucleus, we measured the shape and the stiffness of isolated nuclei and nuclei in living myocytes during disruption of cytoskeletal, myofibrillar, and chromatin structure. We found that the nucleus in myocytes is subject to both tensional and compressional prestress and its deformability is determined by a balance of those opposing forces. By developing a computational model of the prestressed nucleus, we showed that cytoskeletal and chromatin prestresses create vulnerability in the nuclear envelope. Our studies suggest the cytoskeletal-nuclear-chromatin interconnectivity may play an important role in mechanics of myocyte contraction and in the development of laminopathies by lamin mutations. © 2015 by the Society for Experimental Biology and Medicine.

  15. The role of nuclear shapes in nuclear structure (from the perspective of the Daresbury Tandem)

    SciTech Connect

    Nazarewicz, W.

    1993-06-01

    In specific regions of the nuclear periodic chart, large multipole moments are observed and the low-lying excitations have a rotational character. These features are understood if the nuclei in question are assumed to have a stable deformation, i.e., a non-spherical distribution of the nuclear matter. In other (transitional) regions the quasi-rotational bands are present; they are strongly coupled to low-lying vibrational modes. Those nuclei are best understood in terms of small static deformations but large dynamic fluctuations around local equilibria. As a matter of fact, the vast majority of nuclei are deformed; even in those which are spherical or almost spherical, the dynamical couplings to shape vibrations are crucial. The issue of nuclear deformation is many-faceted. If the nuclear shape (nuclear mean field) is deformed, characteristic excitation modes are present, such as rotations and vibrations built upon the non-spherical equilibrium. Through the particle-core coupling, nuclear deformations can dramatically influence the single-particle properties of nucleons moving in the average nuclear potential. Many experimental investigations using the Daresbury Tandem were related in one way or another to the physics of nuclear shapes. Fundamental discoveries from Daresbury include the observation of superdeformed structures in rapidly rotating nuclei, the observation of identical ({open_quotes}twinned{close_quotes}) rotational bands, various studies of structural changes induced by very fast rotation (band-crossings, band-terminations), the observation of the oblate-deformed {open_quotes}dipole{close_quotes} bands, studies of reflection-asymmetric shapes, studies of (quasimolecular) cluster configurations in light nuclei, and many, many others. The author reviews the forefront research at Daresbury from the global perspective; the common denominator being the nuclear shape deformation.

  16. Shape coexistence and isomeric states in neutron-rich Tc112 and Tc113

    NASA Astrophysics Data System (ADS)

    Bruce, A. M.; Lalkovski, S.; Denis Bacelar, A. M.; Górska, M.; Pietri, S.; Podolyák, Zs.; Shi, Y.; Walker, P. M.; Xu, F. R.; Bednarczyk, P.; Cáceres, L.; Casarejos, E.; Cullen, I. J.; Doornenbal, P.; Farrelly, G. F.; Garnsworthy, A. B.; Geissel, H.; Gelletly, W.; Gerl, J.; Grębosz, J.; Hinke, C.; Ilie, G.; Jaworski, G.; Kojouharov, I.; Kurz, N.; Myalski, S.; Palacz, M.; Prokopowicz, W.; Regan, P. H.; Schaffner, H.; Steer, S.; Tashenov, S.; Wollersheim, H. J.

    2010-10-01

    Isomeric states in Tc112 and Tc113, with half-lives of 150(17) ns and 500(100) ns, respectively, have been observed following the relativistic fission of U238. The fission fragments have been separated in a fragment separator and identified by means of energy-loss and time-of-flight techniques. In both nuclei, the ground-state configuration is calculated to have an oblate shape and the isomerism is proposed to arise due to transitions from a triaxial excited state to a low-lying oblate state.

  17. Cytoskeletal prestress regulates nuclear shape and stiffness in cardiac myocytes

    PubMed Central

    Lee, Hyungsuk; Adams, William J; Alford, Patrick W; McCain, Megan L; Feinberg, Adam W; Sheehy, Sean P; Goss, Josue A

    2015-01-01

    Mechanical stresses on the myocyte nucleus have been associated with several diseases and potentially transduce mechanical stimuli into cellular responses. Although a number of physical links between the nuclear envelope and cytoplasmic filaments have been identified, previous studies have focused on the mechanical properties of individual components of the nucleus, such as the nuclear envelope and lamin network. The mechanical interaction between the cytoskeleton and chromatin on nuclear deformability remains elusive. Here, we investigated how cytoskeletal and chromatin structures influence nuclear mechanics in cardiac myocytes. Rapid decondensation of chromatin and rupture of the nuclear membrane caused a sudden expansion of DNA, a consequence of prestress exerted on the nucleus. To characterize the prestress exerted on the nucleus, we measured the shape and the stiffness of isolated nuclei and nuclei in living myocytes during disruption of cytoskeletal, myofibrillar, and chromatin structure. We found that the nucleus in myocytes is subject to both tensional and compressional prestress and its deformability is determined by a balance of those opposing forces. By developing a computational model of the prestressed nucleus, we showed that cytoskeletal and chromatin prestresses create vulnerability in the nuclear envelope. Our studies suggest the cytoskeletal–nuclear–chromatin interconnectivity may play an important role in mechanics of myocyte contraction and in the development of laminopathies by lamin mutations. PMID:25908635

  18. Isomer Shift and Magnetic Moment of the Long-Lived 1/2^{+} Isomer in _{30}^{79}Zn_{49}: Signature of Shape Coexistence near ^{78}Ni.

    PubMed

    Yang, X F; Wraith, C; Xie, L; Babcock, C; Billowes, J; Bissell, M L; Blaum, K; Cheal, B; Flanagan, K T; Garcia Ruiz, R F; Gins, W; Gorges, C; Grob, L K; Heylen, H; Kaufmann, S; Kowalska, M; Kraemer, J; Malbrunot-Ettenauer, S; Neugart, R; Neyens, G; Nörtershäuser, W; Papuga, J; Sánchez, R; Yordanov, D T

    2016-05-06

    Collinear laser spectroscopy is performed on the _{30}^{79}Zn_{49} isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in ^{79}Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I=9/2 and I=1/2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (^{79}Zn)=-1.1866(10)μ_{N}, confirms the spin-parity 9/2^{+} with a νg_{9/2}^{-1} shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (^{79m}Zn)=-1.0180(12)μ_{N} supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ⟨r_{c}^{2}⟩^{79,79m}=+0.204(6)  fm^{2}, providing first evidence of shape coexistence.

  19. Shape coexistence at N=20 and N=28: Study of 0{sub 2}{sup +} states in {sup 34}Si and {sup 44}S

    SciTech Connect

    Grévy, S.; Rotaru, F.; Negoita, F.; Borcea, C.; Borcea, R.; Buta, A.; Calinescu, S.; Petrone, C.; Mrazek, J.; Lukyanov, S.; Penionzhkevich, Y.; Cáceres, L.; De Oliveira, F.; Force, C.; Lebhertz, D.; Sorlin, O.; Stodel, C.; Thomas, J. C.; Chevrier, R. [Grand Accélérateur National d'Ions Lourds , CEA and others

    2014-08-14

    It is well known that the nuclear shell structure changes for the most exotic nuclei. One of the consequences of this phenomenon is the modification of the 'classical' magic numbers, as experimentally observed at N = 20 and N = 28. Nevertheless, the mechanisms responsible for such changes are still under discussion and more experimental information is needed to better constrain the theoretical models. In these proceedings, we report on the discovery and the experimental study by precise spectroscopy experiments of the 0{sub 2}{sup +} state in {sup 34}Si and {sup 44}S. The {sup 34}Si is located between the magic spherical {sup 36}S and the deformed {sup 32}Mg, member of the so-called island of inversion, whereas {sup 44}S is located between the magic spherical {sup 48}Ca and the deformed {sup 42}Si. Therefore, the structure of these nuclei, and in particular the phenomenon of shape coexistence, is of crucial importance to understand how the intruder configurations progressively dominate the ground state structure of the most exotic nuclei at both N = 20 and N = 28.

  20. Isomer Shift and Magnetic Moment of the Long-Lived 1 /2+ Isomer in 30,79Zn49: Signature of Shape Coexistence near 78Ni

    NASA Astrophysics Data System (ADS)

    Yang, X. F.; Wraith, C.; Xie, L.; Babcock, C.; Billowes, J.; Bissell, M. L.; Blaum, K.; Cheal, B.; Flanagan, K. T.; Garcia Ruiz, R. F.; Gins, W.; Gorges, C.; Grob, L. K.; Heylen, H.; Kaufmann, S.; Kowalska, M.; Kraemer, J.; Malbrunot-Ettenauer, S.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Papuga, J.; Sánchez, R.; Yordanov, D. T.

    2016-05-01

    Collinear laser spectroscopy is performed on the 30,79Zn49 isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in 79Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I =9 /2 and I =1 /2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (79Zn)=-1.1866 (10 )μN , confirms the spin-parity 9 /2+ with a ν g9/2 -1 shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (Znm79)=-1.0180 (12 )μN supports a positive parity for the isomer, with a wave function dominated by a 2 h -1 p neutron excitation across the N =50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ ⟨rc2⟩79 ,79 m=+0.204 (6 ) fm2 , providing first evidence of shape coexistence.

  1. Superdeformation in the a Approximately 190 Mass Region and Shape Coexistence in LEAD-194

    NASA Astrophysics Data System (ADS)

    Brinkman, Matthew James

    Near-yrast states in ^{194 }Pb have been identified up to a spin of {~}35hbar following the ^{176}Yb(^ {24}Mg,6n)^{194} Pb^{*} reaction at a beam energy of 134 MeV, measured with the High Energy -Resolution Array located at the Lawrence Berkeley Laboratory 88-Inch Cyclotron facility. Eighteen new transitions were placed. Examples of non-collective prolate and oblate and collective oblate excitations are seen. In addition a rotational band consisting of twelve transitions, with energy spacings characteristic of superdeformed shapes, were also seen. These results have been interpreted using both Nilsson model calculations and previously published potential energy surface calculations. The superdeformed bands in the A ~ 190 mass region are discussed with primary emphasis on ten superdeformed bands in ^{192,193,194 }Hg and ^{192,194,196,198 }Pb discovered or codiscovered by our collaboration. The discussion of superdeformation in these nuclei have been broken into three portions, focusing on the population of, the physics associated with, and the depopulation of these bands, respectively. The population behavior of the superdeformed structures is presented, and discussed with respect to theoretical predictions for nuclei near A ~ 190 expected to support superdeformation. A detailed analysis of the population of the ^{193} Hg^{rm 1a} band is provided, and the results are compared with statistical model calculations predictions. Significant differences were found between the population of the superdeformed bands in the A ~ 150 and 190 mass regions. The systematics of the intraband region are presented. Nilsson model calculations are carried out, with nucleon configurations for the primary superdeformed bands proposed. A discussion of possible mechanisms for reproducing the smooth increase in dynamic moments of inertia observed in all superdeformed bands in this mass region is provided. A number of superdeformed bands in the A ~ 190 mass region have transition energies

  2. Deformation and shape coexistence in 66,70Ni and 69,71Cu nuclei near N = 40

    NASA Astrophysics Data System (ADS)

    Walters, W. B.; Harker, J.; Chiara, C. J.; Janssens, R. V. F.; Albers, M.; Alcorta, M.; Bertone, P. F.; Carpenter, M. P.; Hoffman, C. R.; Kondev, F. G.; Lauritsen, T.; Rogers, A. M.; Seweryniak, D.; Zhu, S.; Broda, R.; Fornal, B.; Krolas, W.; Wrzesinski, J.; Larson, N.; Liddick, S. N.; Prokop, C.; Suchyta, S.; David, H. M.; Doherty, D. T.

    2013-10-01

    New data will be presented for the levels of 66,70Ni and 69,71Cu that extend some of the previously indicated features of deformation and shape coexistence in this region. [R. Broda et al., Phys. Rev. C 86, 064312 (2012)] Excited states in these nuclei were populated through multinucleon-transfer reactions using 70Zn beams provided by the ATLAS facility at ANL. In particular, possible structure associated with the 03+level in 66Ni will be discussed. New levels will be presented in 69,71Cu that extend the 2-particle-1-hole structures to higher energy and spin. [C. J. Chiara et al., Phys. Rev. C 85, 024309 (2012)] Data will be presented that support the placement of a new level in 70Ni at 2912 keV with a spin and parity of (5-). This work was supported by the US DoE under DE-FG02-94-ER40834 & DE-AC02-06CH11357, NNSA DE-NA0000979, and NSF under PHY- 1102511.

  3. Search for shape coexistence in {sup 188,190}Pb via fine structure in the alpha decay of {sup 192,194}Po

    SciTech Connect

    Ahmad, I.; Davids, C.; Janssens, R.V.F.

    1995-08-01

    The interaction between coexisting shapes in nuclei near closed shells was of great interest in the past decade. Excited 0{sup +} states at low energy can often be identified as the bandheads of structures with differing shapes built on those states, These structures were identified in {sup 190-198}Pb via beta decay and alpha decay {open_quotes}fine structure{close_quotes} studies. Coexistence of different shapes in Pb nuclei was predicted by Nilsson-Strutinsky calculations, in which both the oblate and prolate minima were predicted to have excitation energies near 1 MeV. It was our intention to continue the systematic study of the Pb nuclides by searching for excited O{sup +} states in {sup 188}Pb by observing the fine structure in the alpha decay of {sup 192}Po.

  4. Sizing up the nucleus: nuclear shape, size and nuclear-envelope assembly.

    PubMed

    Webster, Micah; Witkin, Keren L; Cohen-Fix, Orna

    2009-05-15

    The nucleus is one of the most prominent cellular organelles, yet surprisingly little is known about how it is formed, what determines its shape and what defines its size. As the nuclear envelope (NE) disassembles in each and every cell cycle in metazoans, the process of rebuilding the nucleus is crucial for proper development and cell proliferation. In this Commentary, we summarize what is known about the regulation of nuclear shape and size, and highlight recent findings that shed light on the process of building a nucleus, including new discoveries related to NE assembly and the relationship between the NE and the endoplasmic reticulum (ER). Throughout our discussion, we note interesting aspects of nuclear structure that have yet to be resolved. Finally, we present an idea - which we refer to as ;the limited flat membrane hypothesis' - to explain the formation of a single nucleus that encompasses of all of the cell's chromosomes following mitosis.

  5. Nuclear shape evolution based on microscopic level densities

    NASA Astrophysics Data System (ADS)

    Ward, D. E.; Carlsson, B. G.; Døssing, T.; Möller, P.; Randrup, J.; Åberg, S.

    2017-02-01

    By combining microscopically calculated level densities with the Metropolis walk method, we develop a consistent framework for treating the energy and angular-momentum dependence of the nuclear shape evolution in the fission process. For each nucleus under consideration, the level density is calculated microscopically for each of more than five million shapes with a recently developed combinatorial method. The method employs the same single-particle levels as those used for the extraction of the pairing and shell contributions to the macroscopic-microscopic potential-energy surface. Containing no new parameters, the treatment is suitable for elucidating the energy dependence of the dynamics of warm nuclei on pairing and shell effects. It is illustrated for the fission fragment mass distribution for several uranium and plutonium isotopes of particular interest.

  6. Monopole strength as a probe of nuclear shape mixing

    SciTech Connect

    Meyer, R.A.

    1987-08-17

    The monopole strength, MS, within a single set of nuclear shape excitations is compared with the MS between different shapes. After misconceptions are pointed out concerning the spin dependence of B(E2) values, MS properties are juxtaposed with gamma-ray and beta-decay properties of /sup 70/Se, /sup 96/Zr, /sup 102/Pd, and the N = 60 isotones to illustrate the utility of combined investigations and evidence is given for the observation of a two-phonon octupole multiplet. Finally, consideration is given to the dominance of the /sup 3/S/sub 1/ force in producing deformation in the N > 50 1g nuclei. 23 refs., 4 figs.

  7. Nuclear export of RNA: Different sizes, shapes and functions.

    PubMed

    Williams, Tobias; Ngo, Linh H; Wickramasinghe, Vihandha O

    2017-09-01

    Export of protein-coding and non-coding RNA molecules from the nucleus to the cytoplasm is critical for gene expression. This necessitates the continuous transport of RNA species of different size, shape and function through nuclear pore complexes via export receptors and adaptor proteins. Here, we provide an overview of the major RNA export pathways in humans, highlighting the similarities and differences between each. Its importance is underscored by the growing appreciation that deregulation of RNA export pathways is associated with human diseases like cancer. Copyright © 2017. Published by Elsevier Ltd.

  8. Shape and topography corrections for planetary nuclear spectroscopy

    NASA Astrophysics Data System (ADS)

    Prettyman, Thomas H.; Hendricks, John S.

    2015-11-01

    The elemental composition of planetary surfaces can be determined using gamma ray and neutron spectroscopy. Most planetary bodies for which nuclear spectroscopy data have been acquired are round, and simple, analytic corrections for measurement geometry can be applied; however, recent measurements of the irregular asteroid 4 Vesta by Dawn required more detailed corrections using a shape model (Prettyman et al., Science 2012). In addition, subtle artifacts of topography have been observed in low altitude measurements of lunar craters, with potential implications for polar hydrogen content (Eke et al., JGR 2015). To explore shape and topography effects, we have updated the general-purpose Monte Carlo radiation transport code MCNPX to include a polygonal shape model (Prettyman and Hendricks, LPSC 2015). The shape model is fully integrated with the code’s 3D combinatorial geometry modules. A voxel-based acceleration algorithm enables fast ray-intersection calculations needed for Monte Carlo. As modified, MCNPX can model neutron and gamma ray transport within natural surfaces using global and/or regional shape/topography data (e.g. from photogrammetry and laser altimetry). We are using MCNPX to explore the effect of small-scale roughness, regional-, and global-topography for asteroids, comets and close-up measurements of high-relief features on larger bodies, such as the lunar surface. MCNPX can characterize basic effects on measurements by an orbiting spectrometer such as 1) the angular distribution of emitted particles, 2) shielding of galactic cosmic rays by surrounding terrain and 3) re-entrant scattering. In some cases, re-entrant scattering can be ignored, leading to a fast ray-tracing model that treats effects 1 and 2. The algorithm is applied to forward modeling and spatial deconvolution of epithermal neutron data acquired at Vesta. Analyses of shape/topography effects and correction strategies are presented for Vesta, selected small bodies and cratered

  9. Fourier expansion of deformed nuclear shapes expressed as the deviation from a spheroid

    NASA Astrophysics Data System (ADS)

    Pomorski, K.; Nerlo-Pomorska, B.; Bartel, J.

    2017-06-01

    A Fourier decomposition of nuclear shapes is proposed and shown to be able to cover a very wide range of nuclear deformations up to the scission point. This Fourier shape parametrization is applied to the deviations of a nuclear liquid-drop profile from a spheroidal shape. It is shown that such a shape profile expansion is not only very rapidly converging, but also gives an excellent description of nuclear shapes all along the path to fission. Some examples of the liquid-drop and the macroscopic-microscopic potential energy surfaces in this new shape parametrization are presented and the connection with Bohr (β ,γ ) deformation parameters is given.

  10. Nuclear envelope structural proteins facilitate nuclear shape changes accompanying embryonic differentiation and fidelity of gene expression.

    PubMed

    Smith, Elizabeth R; Meng, Yue; Moore, Robert; Tse, Jeffrey D; Xu, Arn G; Xu, Xiang-Xi

    2017-01-14

    Nuclear size and shape are specific to a cell type, function, and location, and can serve as indicators of disease and development. We previously found that lamin A/C and associated nuclear envelope structural proteins were upregulated when murine embryonic stem (ES) cells differentiated to primitive endoderm cells. Here we further investigated the morphological changes of nuclei that accompany this differentiation. The nuclei of undifferentiated wild type cells were found shaped as flattened, irregular ovals, whereas nuclei of Gata4-positive endoderm cells were more spherical, less flattened, and with a slightly reduced volume. The morphological change was confirmed in the trophectoderm and primitive endoderm lineages of E4.5 blastocysts, compared to larger and more irregularly shaped of the nuclei of the inner cell mass. We established ES cells genetically null for the nuclear lamina proteins lamin A/C or the inner nuclear envelope protein emerin, or compound mutant for both lamin A/C and emerin. ES cells deficient in lamin A/C differentiated to endoderm but less efficiently, and the nuclei remained flattened and failed to condense. The size and shape of emerin-deficient nuclei also remained uncondensed after treatment with RA. The emerin/lamin A/C double knockout ES cells failed to differentiate to endoderm cells, though the nuclei condensed but retained a generally flattened ellipsoid shape. Additionally, ES cells deficient for lamin A/C and/or emerin had compromised ability to undergo endoderm differentiation, where the differentiating cells often exhibited coexpression of pluripotent and differentiation markers, such as Oct3/4 and Gata4, respectively, indicating an infidelity of gene regulation. The results suggest that changes in nuclear size and shape, which are mediated by nuclear envelope structural proteins lamin A/C and/or emerin, also impact gene regulation and lineage differentiation in early embryos. Nevertheless, mice lacking both lamin A/C and

  11. Nuclear structure of 96,98Mo: Shape coexistence and mixed-symmetry states

    NASA Astrophysics Data System (ADS)

    Thomas, T.; Werner, V.; Jolie, J.; Nomura, K.; Ahn, T.; Cooper, N.; Duckwitz, H.; Fitzler, A.; Fransen, C.; Gade, A.; Hinton, M.; Ilie, G.; Jessen, K.; Linnemann, A.; Petkov, P.; Pietralla, N.; Radeck, D.

    2016-03-01

    Excited low-spin states in 96Mo and 98Mo have been studied in γγ angular correlation experiments in order to determine spins and multipole mixing ratios. Furthermore, from a Doppler lineshape analysis effective lifetimes τ in the femtosecond range were obtained. The experimental data show a complex spectrum due to configuration mixing, which is confirmed by Interacting Boson Model calculations based on a Skyrme energy density functional. The M1-transition strengths of transitions depopulating excited 2+ states to the first 2+ state are discussed in terms of the proton-neutron mixed symmetry.

  12. Shape analysis of giant vesicles with fluid phase coexistence by laser scanning microscopy to determine curvature, bending elasticity, and line tension.

    PubMed

    Hess, Samuel T; Gudheti, Manasa V; Mlodzianoski, Michael; Baumgart, Tobias

    2007-01-01

    Membrane shape parameters such as curvature, bending elasticity, and lateral tension, are relevant to the lateral organization and function of biomembranes, and may critically influence the formation of lateral clustering patterns observed in living cells. Fluorescence laser-scanning microscopy can be used to image vesicles and cell membranes, and from shape analysis of these images mechanical membrane parameters can be quantified. Methods to analyze images of equatorial sections obtained by confocal or multiphoton microscopy are detailed, in order to estimate curvature, lateral tension, line tension, relative differences in mean curvature and Gaussian curvature bending moduli, and fluorescence dye intensity profiles, typically within coexisting liquid-ordered and liquid-disordered membrane domains. A variety of shape tracing and shape fitting methods are compared.

  13. Allometric and Non-Allometric Patterns in Sexual Dimorphism Discrimination of Wing Shape in Ophion intricatus: Might Two Male Morphotypes Coexist?

    PubMed Central

    Benítez, Hugo A.; Bravi, Raffaella; Parra, Luis E.; Sanzana, Maria-Jose; Sepúlveda-Zúñiga, Einer

    2013-01-01

    Bees and wasps could exhibit shape and size sexual dimorphism, and most of their morphological variation could depend on phenotypic responses due to environmental pressure during ontogenetic development. More complex measurement techniques related to size and shape rather than simply to mass and length should be required to analyze such a complex sexual dimorphism. In this study, differences related to wing shape and size of males and females of Ophion intricatus Brullé (Hymenoptera: Ichneumonidae) were evaluated using geometric morphometrics. Right and left wings of specimens were used, and a photographic matrix was constructed in which 18 morphological landmarks based on shape and vein patterns of the wings were digitalized. A multivariate analysis of wing shape showed significant differences between sexes and sites. The geometric variation demonstrated that the points at the intersection of radial and cubital-anal veins might be key characters to differentiate between sexes. This study also showed the presence of two clearly different male morphotypes coexisting in the same study site. However, it should be noted that the results of this study showed that the variation in wing shape is an analytical character in the determination of sexual differences in the family Ichneumonidae. These differences raise the question of whether sexual dimorphism of wing shape may be modulated by natural selection. PMID:24766555

  14. Shape coexistence in the N = 19 neutron-rich nucleus 31Mg explored by β-γ spectroscopy of spin-polarized 31Na

    NASA Astrophysics Data System (ADS)

    Nishibata, H.; Shimoda, T.; Odahara, A.; Morimoto, S.; Kanaya, S.; Yagi, A.; Kanaoka, H.; Pearson, M. R.; Levy, C. D. P.; Kimura, M.

    2017-04-01

    The structure of excited states in the neutron-rich nucleus 31Mg, which is in the region of the "island of inversion" associated with the neutron magic number N = 20, is studied by β-γ spectroscopy of spin-polarized 31Na. Among the 31Mg levels below the one neutron separation energy of 2.3 MeV, the spin values of all five positive-parity levels are unambiguously determined by observing the anisotropic β decay. Two rotational bands with Kπ = 1 /2+ and 1 /2- are proposed based on the spins and energies of the levels. Comparison on a level-by-level basis is performed between the experimental results and theoretical calculations by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM). It is found that various nuclear structures coexist in the low excitation energy region in 31Mg.

  15. Shape coexistence in the neutron-deficient even-even (182-188)Hg isotopes studied via coulomb excitation.

    PubMed

    Bree, N; Wrzosek-Lipska, K; Petts, A; Andreyev, A; Bastin, B; Bender, M; Blazhev, A; Bruyneel, B; Butler, P A; Butterworth, J; Carpenter, M P; Cederkäll, J; Clément, E; Cocolios, T E; Deacon, A; Diriken, J; Ekström, A; Fitzpatrick, C; Fraile, L M; Fransen, Ch; Freeman, S J; Gaffney, L P; García-Ramos, J E; Geibel, K; Gernhäuser, R; Grahn, T; Guttormsen, M; Hadinia, B; Hadyńska-Kle K, K; Hass, M; Heenen, P-H; Herzberg, R-D; Hess, H; Heyde, K; Huyse, M; Ivanov, O; Jenkins, D G; Julin, R; Kesteloot, N; Kröll, Th; Krücken, R; Larsen, A C; Lutter, R; Marley, P; Napiorkowski, P J; Orlandi, R; Page, R D; Pakarinen, J; Patronis, N; Peura, P J; Piselli, E; Rahkila, P; Rapisarda, E; Reiter, P; Robinson, A P; Scheck, M; Siem, S; Singh Chakkal, K; Smith, J F; Srebrny, J; Stefanescu, I; Tveten, G M; Van Duppen, P; Van de Walle, J; Voulot, D; Warr, N; Wenander, F; Wiens, A; Wood, J L; Zielińska, M

    2014-04-25

    Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85  MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.

  16. The shapes of nuclei

    NASA Astrophysics Data System (ADS)

    Bertsch, G. F.

    Gerry Brown initiated some early studies on the coexistence of different nuclear shapes. The subject has continued to be of interest and is crucial for understanding nuclear fission. We now have a very good picture of the potential energy surface with respect to shape degrees of freedom in heavy nuclei, but the dynamics remain problematic. In contrast, the early studies on light nuclei were quite successful in describing the mixing between shapes. Perhaps a new approach in the spirit of the old calculations could better elucidate the character of the fission dynamics and explain phenomena that current theory does not model well.

  17. Shape Coexistence Near Neutron Number N=20: First Identification of the E0 Decay from the Deformed First Excited J{sup p}i=0{sup +} State in {sup 30}Mg

    SciTech Connect

    Schwerdtfeger, W.; Thirolf, P. G.; Wimmer, K.; Habs, D.; Hertenberger, R.; Lutter, R.; Morgan, T.; Mach, H.; Rodriguez, T. R.; Egido, J. L.; Bildstein, V.; Gernhaeuser, R.; Kroell, T.; Kruecken, R.; Ring, P.; Fraile, L. M.; Heyde, K.; Hoff, P.; Huebel, H.; Koester, U.

    2009-07-03

    The 1789 keV state in {sup 30}Mg was identified as the first excited 0{sup +} state via its electric monopole (E0) transition to the ground state. The measured small value of rho{sup 2}(E0,0{sub 2}{sup +}->0{sub 1}{sup +})=(26.2+-7.5)x10{sup -3} implies within a two-level model a small mixing of competing configurations with largely different intrinsic quadrupole deformation near the neutron shell closure at N=20. Axially symmetric configuration mixing calculations identify the ground state of {sup 30}Mg to be based on neutron configurations below the N=20 shell closure, while the excited 0{sup +} state mainly consists of two neutrons excited into the nu 1f{sub 7/2} orbital. The experimental result represents the first case where an E0 back decay from a strongly deformed second to the normal deformed first nuclear potential minimum well has been unambiguously identified, thus directly proving shape coexistence at the borderline of the much-debated 'island of inversion.'

  18. Mitochondrial and nuclear DNA matching shapes metabolism and healthy ageing.

    PubMed

    Latorre-Pellicer, Ana; Moreno-Loshuertos, Raquel; Lechuga-Vieco, Ana Victoria; Sánchez-Cabo, Fátima; Torroja, Carlos; Acín-Pérez, Rebeca; Calvo, Enrique; Aix, Esther; González-Guerra, Andrés; Logan, Angela; Bernad-Miana, María Luisa; Romanos, Eduardo; Cruz, Raquel; Cogliati, Sara; Sobrino, Beatriz; Carracedo, Ángel; Pérez-Martos, Acisclo; Fernández-Silva, Patricio; Ruíz-Cabello, Jesús; Murphy, Michael P; Flores, Ignacio; Vázquez, Jesús; Enríquez, José Antonio

    2016-07-28

    Human mitochondrial DNA (mtDNA) shows extensive within population sequence variability. Many studies suggest that mtDNA variants may be associated with ageing or diseases, although mechanistic evidence at the molecular level is lacking. Mitochondrial replacement has the potential to prevent transmission of disease-causing oocyte mtDNA. However, extension of this technology requires a comprehensive understanding of the physiological relevance of mtDNA sequence variability and its match with the nuclear-encoded mitochondrial genes. Studies in conplastic animals allow comparison of individuals with the same nuclear genome but different mtDNA variants, and have provided both supporting and refuting evidence that mtDNA variation influences organismal physiology. However, most of these studies did not confirm the conplastic status, focused on younger animals, and did not investigate the full range of physiological and phenotypic variability likely to be influenced by mitochondria. Here we systematically characterized conplastic mice throughout their lifespan using transcriptomic, proteomic,metabolomic, biochemical, physiological and phenotyping studies. We show that mtDNA haplotype profoundly influences mitochondrial proteostasis and reactive oxygen species generation,insulin signalling, obesity, and ageing parameters including telomere shortening and mitochondrial dysfunction, resulting in profound differences in health longevity between conplastic strains.

  19. Function of nuclear membrane proteins in shaping the nuclear envelope integrity during closed mitosis.

    PubMed

    Yang, Hui-Ju; Iwamoto, Masaaki; Hiraoka, Yasushi; Haraguchi, Tokuko

    2017-04-08

    The nuclear envelope (NE) not only protects the genome from being directly accessed by detrimental agents but also regulates genome organization. Breaches in NE integrity threaten genome stability and impede cellular function. Nonetheless, the NE constantly remodels, and NE integrity is endangered in dividing or differentiating cells. Specifically, in unicellular eukaryotes undergoing closed mitosis, the NE expands instead of breaking down during chromosome segregation. The newly assembling nuclear pore complexes (NPCs) penetrate the existing NE in interphase. A peculiar example of NE remodeling during nuclear differentiation in Tetrahymena involves formation of the redundant NE and clustered NPCs. Even under these conditions, the NE remains intact. Many recent studies on unicellular organisms have revealed that nuclear membrane proteins, such as LEM-domain proteins, play a role in maintaining NE integrity. This review summarizes and discusses how nuclear membrane proteins participate in NE integrity.

  20. Textual and shape-based feature extraction and neuro-fuzzy classifier for nuclear track recognition

    NASA Astrophysics Data System (ADS)

    Khayat, Omid; Afarideh, Hossein

    2013-04-01

    Track counting algorithms as one of the fundamental principles of nuclear science have been emphasized in the recent years. Accurate measurement of nuclear tracks on solid-state nuclear track detectors is the aim of track counting systems. Commonly track counting systems comprise a hardware system for the task of imaging and software for analysing the track images. In this paper, a track recognition algorithm based on 12 defined textual and shape-based features and a neuro-fuzzy classifier is proposed. Features are defined so as to discern the tracks from the background and small objects. Then, according to the defined features, tracks are detected using a trained neuro-fuzzy system. Features and the classifier are finally validated via 100 Alpha track images and 40 training samples. It is shown that principle textual and shape-based features concomitantly yield a high rate of track detection compared with the single-feature based methods.

  1. Nuclear structure and shapes from prompt gamma ray spectroscopy of fission products

    SciTech Connect

    Ahmad, I.; Morss, L.R.; Durell, J.L.

    1996-10-01

    Many nuclear shape phenomena are predicted to occur in neutron-rich nuclei. The best source for the production of these nuclides is the spontaneous fission which produces practically hundreds of nuclides with yields of greater than 0.1 % per decay. Measurements of coincident gamma rays with large Ge arrays have recently been made to obtain information on nuclear structures and shapes of these neutron- rich nuclei. Among the important results that have been obtained from such measurements are octupole correlations in Ba isotopes, triaxial shapes in Ru nuclei, two-phonon vibrations in {sup 106}Mo and level lifetimes and quadrupole moments in Nd isotopes and A=100 nuclei. These data have been used to test theoretical models.

  2. The role of belief systems in shaping nuclear weapons policy preference and thinking in Brazil

    SciTech Connect

    Krasno, J.E.C.

    1994-12-31

    This study examines motivations behind the decisions of national leaders to pursue or not to pursue the development of nuclear weapons. The research, which builds upon work done in the field of Political Psychology, was conducted in Brazil and focuses on the role that belief systems play in shaping policy preferences and thinking by members of the Brazilian elite on nuclear issues. The data were gathered in Brazil through in-depth interviews and a questionnaire administered to members of the Brazilian elite who be- long to groups which have input in forming policy. Proliferation studies, generally, have concentrated on the acquisition of nuclear technology and have rarely studied motivations which contribute to the demand for these weapons. Research on beliefs and policy formation suggests that beliefs and values should be expected to play a role in shaping nuclear policy. The results show that beliefs about status, power, competition, and moral considerations do correlate very significantly with policy thinking on nuclear issues and therefore sustain the hypothesis of this study. However, the findings on worldview do not significantly correlate with nuclear policy thinking and therefore do not sustain the prevailing hypothesis on that relationship.

  3. Coexistence of nuclear DNA-encoded tRNAVal(AAC) and mitochondrial DNA-encoded tRNAVal(UAC) in mitochondria of a liverwort Marchantia polymorpha.

    PubMed Central

    Akashi, K; Takenaka, M; Yamaoka, S; Suyama, Y; Fukuzawa, H; Ohyama, K

    1998-01-01

    The liverwort Marchantia polymorpha mitochondrial DNA encodes almost all tRNAs required for mitochondrial translation except for the isoleucine (AUU, AUC) and threonine (ACA, ACG) codons, while the missing tRNAs are supplied in part by the nucleus and imported in mitochondria. In this paper, we report a finding of two radically different nuclear tRNAVal(AAC) genes and import of the corresponding tRNA isoacceptors in M.polymorpha mitochondria. This finding is surprising since the mtDNA encodes the gene for tRNAVal(UAC), which alone was considered sufficient for translating all four valine codons GUN by the U/N wobble mechanism. The present results suggest for the first time that the import of ncDNA-encoded tRNAs may result in decoding overlaps in plant mitochondria. The coexistence of nuclear DNA-encoded tRNAVal(AAC) and mitochondrial DNA-encoded tRNAVal(UAC) in liverwort mitochondria and the significance for the decoding mechanism as well as evolution of tRNA import are discussed. PMID:9547276

  4. Position control of active magnetic levitation using sphere-shaped HTS bulk for inertial nuclear fusion

    NASA Astrophysics Data System (ADS)

    Suga, K.; Riku, K.; Agatsuma, K.; Ueda, H.; Ishiyama, A.

    2008-02-01

    We have developed an active magnetic levitation system that comprises a field-cooled disk-shaped or sphere-shaped HTS bulk and multiple ring-shaped electromagnets. In this system, the levitation height of HTS bulk can be controlled by adjusting the operating current of each electromagnet individually. Further, the application of the vertical noncontact levitation system is expected due to its levitation stability without mechanical supports. We assume that this system is applied to inertial nuclear fusion. However, one of the important issues is to achieve position control with high accuracy of the fusion fuel in order to illuminate the target evenly over the entire surface. Therefore, this system is applied to the levitation and position control of a sphere-shaped superconducting capsule containing nuclear fusion fuel. In this study, we designed and constructed a position control system for the sphere-shaped HTS bulk with a diameter of 5 mm by using numerical simulation based on hybrid finite element and boundary element analysis. We then carried out the experiment of levitation height and position control characteristics of the HTS bulk in this system. With regard to position control, accuracies within 59 ?m are obtained.

  5. System for determining the type of nuclear radiation from detector output pulse shape

    DOEpatents

    Miller, William H.; Berliner, Ronald R.

    1994-01-01

    A radiation detection system determines the type of nuclear radiation received in a detector by producing a correlation value representative of the statistical cross correlation between the shape of the detector signal and pulse shape data previously stored in memory and characteristic of respective types of radiation. The correlation value is indicative of the type of radiation. The energy of the radiation is determined from the detector signal and is used to produce a spectrum of radiation energies according to radiation type for indicating the nature of the material producing the radiation.

  6. System for determining the type of nuclear radiation from detector output pulse shape

    DOEpatents

    Miller, W.H.; Berliner, R.R.

    1994-09-13

    A radiation detection system determines the type of nuclear radiation received in a detector by producing a correlation value representative of the statistical cross correlation between the shape of the detector signal and pulse shape data previously stored in memory and characteristic of respective types of radiation. The correlation value is indicative of the type of radiation. The energy of the radiation is determined from the detector signal and is used to produce a spectrum of radiation energies according to radiation type for indicating the nature of the material producing the radiation. 2 figs.

  7. Probing nuclear dynamics in jet production with a global event shape

    NASA Astrophysics Data System (ADS)

    Kang, Zhong-Bo; Liu, Xiaohui; Mantry, Sonny; Qiu, Jian-Wei

    2013-10-01

    We study single jet production in electron-nucleus collisions e-+NA→J+X, using the 1-jettiness (τ1) global event shape. It inclusively quantifies the pattern of radiation in the final state, gives enhanced sensitivity to soft radiation at wide angles from the nuclear beam and final-state jet, and facilitates the resummation of large Sudakov logarithms associated with the veto on additional jets. Through their effect on the observed pattern of radiation, 1-jettiness can be a useful probe of nuclear parton distribution functions and power corrections from dynamical effects in the nuclear medium. This formalism allows for the standard jet shape analysis while simultaneously providing sensitivity to soft radiation at wide angles from the jet. We use a factorization framework for cross-sections differential in τ1 and the transverse momentum (PJT) and rapidity (y) of the jet, in the region τ1≪PJT. The restriction τ1≪PJT allows only soft radiation between the nuclear beam and jet directions, thereby acting as a veto on additional jets. This region is also insensitive to the details of the jet algorithm, allowing for better theoretical control over resummation, while providing enhanced sensitivity to nuclear medium effects. We give numerical results at leading twist, with resummation at the next-to-next-to-leading logarithmic level of accuracy, for a variety of nuclear targets. Such studies would be ideal for the electron-ion collider and the LHeC proposals for a future electron-ion collider, where a range of nuclear targets are planned.

  8. Universally Conserved Relationships between Nuclear Shape and Cytoplasmic Mechanical Properties in Human Stem Cells

    PubMed Central

    Lozoya, Oswaldo A.; Gilchrist, Christopher L.; Guilak, Farshid

    2016-01-01

    The ability of cells to proliferate, differentiate, transduce extracellular signals and assemble tissues involves structural connections between nucleus and cytoskeleton. Yet, how the mechanics of these connections vary inside stem cells is not fully understood. To address those questions, we combined two-dimensional particle-tracking microrheology and morphological measures using variable reduction techniques to measure whether cytoplasmic mechanics allow for discrimination between different human adherent stem cell types and across different culture conditions. Here we show that nuclear shape is a quantifiable discriminant of mechanical properties in the perinuclear cytoskeleton (pnCSK) of various stem cell types. Also, we find the pnCSK is a region with different mechanical properties than elsewhere in the cytoskeleton, with heterogeneously distributed locations exhibiting subdiffusive features, and which obeys physical relations conserved among various stem cell types. Finally, we offer a prospective basis to discriminate between stem cell types by coupling perinuclear mechanical properties to nuclear shape. PMID:26976044

  9. 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.

  10. Universally Conserved Relationships between Nuclear Shape and Cytoplasmic Mechanical Properties in Human Stem Cells

    NASA Astrophysics Data System (ADS)

    Lozoya, Oswaldo A.; Gilchrist, Christopher L.; Guilak, Farshid

    2016-03-01

    The ability of cells to proliferate, differentiate, transduce extracellular signals and assemble tissues involves structural connections between nucleus and cytoskeleton. Yet, how the mechanics of these connections vary inside stem cells is not fully understood. To address those questions, we combined two-dimensional particle-tracking microrheology and morphological measures using variable reduction techniques to measure whether cytoplasmic mechanics allow for discrimination between different human adherent stem cell types and across different culture conditions. Here we show that nuclear shape is a quantifiable discriminant of mechanical properties in the perinuclear cytoskeleton (pnCSK) of various stem cell types. Also, we find the pnCSK is a region with different mechanical properties than elsewhere in the cytoskeleton, with heterogeneously distributed locations exhibiting subdiffusive features, and which obeys physical relations conserved among various stem cell types. Finally, we offer a prospective basis to discriminate between stem cell types by coupling perinuclear mechanical properties to nuclear shape.

  11. The Evolution of Air and Nuclear Doctrine: The Theories that Shaped SIOP-62

    DTIC Science & Technology

    2016-06-01

    THE EVOLUTION OF AIR AND NUCLEAR DOCTRINE: THE THEORIES THAT SHAPED SIOP-62 BY DAVID J. WYRICK A THESIS PRESENTED TO THE...success in completing this work. vi ABSTRACT This study analyzes the evolution of Airpower doctrine from 1920- 1962. The key event...Tammy Davis Biddle, Rhetoric and Reality in Air Warfare: The evolution of British and American Ideas about Strategic Bombing, 1914-1945 (Princeton

  12. Periodic orbit bifurcations and local symmetry restorations in exotic-shape nuclear mean fields

    NASA Astrophysics Data System (ADS)

    Arita, Ken-ichiro

    2017-07-01

    The semiclassical origins of the enhancement of shell effects in exotic-shape mean-field potentials are investigated by focusing attention on the roles of the local symmetries associated with the periodic-orbit bifurcations. The deformed shell structures for four types of pure octupole shapes in the nuclear mean-field model having a realistic radial dependence are analyzed. Remarkable shell effects are shown for a large Y 32 deformation having tetrahedral symmetry. Much stronger shell effects found in the shape parametrization smoothly connecting the sphere and the tetrahedron are investigated from the view-point of the classical-quantum correspondence. The local dynamical symmetries associated with the bridge orbit bifurcations are shown to have significant roles in the emergence of exotic deformed shell structures for certain combinations of the surface diffuseness and the tetrahedral deformation parameters.

  13. Coexisting static magnetic order and superconductivity in CeCu sub 2 Si sub 2 found by nuclear quadrupole resonance

    SciTech Connect

    Tien, C. )

    1991-01-01

    {sup 63}Cu nuclear quadrupole resonance (NQR) has been observed in a heavy-fermion system CeCu{sub 2}Si{sub 2}. In the superconducting CeCu{sub 2}Si{sub 2} specimens ({ital T}{sub {ital c}}{congruent}0.6 K), NQR experiments have revealed an onset of a phase transition below {similar to}1 K. Zero- and longitudinal-field muon-spin-relaxation measurements suggest a static magnetic ordering below {similar to}0.8 K, either in the spin-glass or in incommensurate spin-density-wave states. The exotic transition observed in NQR measurements should be closely related to the static magnetic ordering in muon-spin-relaxation measurements. NQR data from a nonsuperconducting CeCu{sub 2}Si{sub 2} sample are consistent with extensive disorder in Cu site occupation. Therefore, the spin-density wave may be depressed in the nonsuperconducting CeCu{sub 2}Si{sub 2}. The superconducting transition temperature {ital T}{sub {ital c}} can be enhanced by the presence of spin-density waves such that, if the spin-density wave is depressed, CeCu{sub 2}Si{sub 2} will lose its superconducting properties.

  14. Mechano-topographic modulation of stem cell nuclear shape on nanofibrous scaffolds.

    PubMed

    Nathan, Ashwin S; Baker, Brendon M; Nerurkar, Nandan L; Mauck, Robert L

    2011-01-01

    Stem cells transit along a variety of lineage-specific routes towards differentiated phenotypes. These fate decisions are dependent not just on the soluble chemical cues that are encountered or enforced in vivo and in vitro, but also on physical cues from the cellular microenvironment. These physical cues can consist of both nano- and micro-scale topographical features, as well as mechanical inputs provided passively (from the base properties of the materials to which they adhere) or actively (from extrinsic applied mechanical deformations). A suitable tool to investigate the coordination of these cues lies in nanofibrous scaffolds, which can both dictate cellular and cytoskeletal orientation and facilitate mechanical perturbation of seeded cells. Here, we demonstrate a coordinated influence of scaffold architecture (aligned vs. randomly organized fibers) and tensile deformation on nuclear shape and orientation. Sensitivity of nuclear morphology to scaffold architecture was more pronounced in stem cell populations than in terminally differentiated fibrochondrocytes. Tension applied to the scaffold elicited further alterations in nuclear morphology, greatest in stem cells, that were mediated by the filamentous actin cytoskeleton, but not the microtubule or intermediate filament network. Nuclear perturbations were time and direction dependent, suggesting that the modality and direction of loading influenced nuclear architecture. The present work may provide additional insight into the mechanisms by which the physical microenvironment influences cell fate decisions, and has specific application to the design of new materials for regenerative medicine applications with adult stem cells. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  15. Identification of Fasciola species based on mitochondrial and nuclear DNA reveals the co-existence of intermediate Fasciola and Fasciola gigantica in Thailand.

    PubMed

    Wannasan, Anchalee; Khositharattanakool, Pathamet; Chaiwong, Prasong; Piangjai, Somsak; Uparanukraw, Pichart; Morakote, Nimit

    2014-11-01

    Molecular techniques were used to identify Fasciola species collected from Chiang Mai Thailand. Morphometrically, 65 stained and 45 fresh worms collected from cattle suggested the possible occurrence of both F. gigantica and F. hepatica. Twenty-two worms comprising 15 from cattle and 7 from human patients, were identified subsequently based on three genetic markers: mitochondrial nicotinamide adenine dinucleotide dehydrogenase subunit 1 (nad1), mitochondrial cytochrome c oxidase subunit 1 (cox1) and nuclear ribosomal internal transcribed spacer 2 (ITS2). All of them presented the F. gigantica type in maternally inherited mitochondrial sequences (nad1 and cox1), with six types in each sequence (FgNDI-CM1 to FgNDI-CM6 and FgCOI-CM1 to FgCOI-CM6, respectively). Remarkably, the predominant nad1 type, FgNDI-CM6, was identical to that of aspermic Fasciola sp. formerly reported from Thailand, Japan, Korea, China, Vietnam, and Myanmar. ITS2 sequences were analyzed successfully in 20 worms. Fifteen worms showed the F. gigantica type and five (including one worm from a patient) had mixed ITS2 sequences of both F. gigantica and F. hepatica in the same worms, with additional heterogeneity within both ITS2 types. This study revealed the intermediate form of Fasciola coexisting with F. gigantica for the first time in Thailand.

  16. Spermatid Head Elongation with Normal Nuclear Shaping Requires ADP-Ribosyltransferase PARP11 (ARTD11) in Mice1

    PubMed Central

    Meyer-Ficca, Mirella L.; Ihara, Motomasa; Bader, Jessica J.; Leu, N. Adrian; Beneke, Sascha; Meyer, Ralph G.

    2015-01-01

    ABSTRACT Sperm are highly differentiated cells characterized by their species-specific nuclear shapes and extremely condensed chromatin. Abnormal head shapes represent a form of teratozoospermia that can impair fertilization capacity. This study shows that poly(ADP-ribose) polymerase-11 (ARTD11/PARP11), a member of the ADP-ribosyltransferase (ARTD) family, is expressed preferentially in spermatids undergoing nuclear condensation and differentiation. Deletion of the Parp11 gene results in teratozoospermia and male infertility in mice due to the formation of abnormally shaped fertilization-incompetent sperm, despite normal testis weights and sperm counts. At the subcellular level, PARP11-deficient elongating spermatids reveal structural defects in the nuclear envelope and chromatin detachment associated with abnormal nuclear shaping, suggesting functional relevance of PARP11 for nuclear envelope stability and nuclear reorganization during spermiogenesis. In vitro, PARP11 exhibits mono(ADP-ribosyl)ation activity with the ability to ADP-ribosylate itself. In transfected somatic cells, PARP11 colocalizes with nuclear pore components, such as NUP153. Amino acids Y77, Q86, and R95 in the N-terminal WWE domain, as well as presence of the catalytic domain, are essential for colocalization of PARP11 with the nuclear envelope, but catalytic activity of the protein is not required for colocalization with NUP153. This study demonstrates that PARP11 is a novel enzyme important for proper sperm head shaping and identifies it as a potential factor involved in idiopathic mammalian teratozoospermia. PMID:25673562

  17. Mito-nuclear genetic comparison in a Wolbachia infected weevil: insights on reproductive mode, infection age and evolutionary forces shaping genetic variation

    PubMed Central

    2010-01-01

    Background Maternally inherited endosymbionts like Wolbachia pipientis are in linkage disequilibrium with the mtDNA of their hosts. Therefore, they can induce selective sweeps, decreasing genetic diversity over many generations. This sex ratio distorter, that is involved in the origin of parthenogenesis and other reproductive alterations, infects the parthenogenetic weevil Naupactus cervinus, a serious pest of ornamental and fruit plants. Results Molecular evolution analyses of mitochondrial (COI) and nuclear (ITS1) sequences from 309 individuals of Naupactus cervinus sampled over a broad range of its geographical distribution were carried out. Our results demonstrate lack of recombination in the nuclear fragment, non-random association between nuclear and mitochondrial genomes and the consequent coevolution of both genomes, being an indirect evidence of apomixis. This weevil is infected by a single Wolbachia strain, which could have caused a moderate bottleneck in the invaded population which survived the initial infection. Conclusions Clonal reproduction and Wolbachia infection induce the coevolution of bacterial, mitochondrial and nuclear genomes. The time elapsed since the Wolbachia invasion would have erased the traces of the demographic crash in the mtDNA, being the nuclear genome the only one that retained the signal of the bottleneck. The amount of genetic change accumulated in the mtDNA and the high prevalence of Wolbachia in all populations of N. cervinus agree with the hypothesis of an ancient infection. Wolbachia probably had great influence in shaping the genetic diversity of N. cervinus. However, it would have not caused the extinction of males, since sexual and asexual infected lineages coexisted until recent times. PMID:21050430

  18. Altering the cellular mechanical force balance results in integrated changes in cell, cytoskeletal and nuclear shape

    NASA Technical Reports Server (NTRS)

    Sims, J. R.; Karp, S.; Ingber, D. E.

    1992-01-01

    Studies were carried out with capillary endothelial cells cultured on fibronectin (FN)-coated dishes in order to analyze the mechanism of cell and nuclear shape control by extracellular matrix (ECM). To examine the role of the cytoskeleton in shape determination independent of changes in transmembrane osmotic pressure, membranes of adherent cells were permeabilized with saponin (25 micrograms/ml) using a buffer that maintains the functional integrity of contractile microfilaments. Real-time videomicroscopic studies revealed that addition of 250 microM ATP resulted in time-dependent retraction and rounding of permeabilized cells and nuclei in a manner similar to that observed in intact living cells following detachment using trypsin-EDTA. Computerized image analysis confirmed that permeabilized cells remained essentially rigid in the absence of ATP and that retraction was stimulated in a dose-dependent manner as the concentration of ATP was raised from 10 to 250 microM. Maximal rounding occurred by 30 min with projected cell and nuclear areas being reduced by 69 and 41%, respectively. ATP-induced rounding was also accompanied by a redistribution of microfilaments resulting in formation of a dense net of F-actin surrounding retracted nuclei. Importantly, ATP-stimulated changes in cell, cytoskeletal, and nuclear form were prevented in permeabilized cells using a synthetic myosin peptide (IRICRKG) that has been previously shown to inhibit actomyosin filament sliding in muscle. In contrast, both the rate and extent of cell and nuclear rounding were increased in permeabilized cells exposed to ATP when the soluble FN peptide, GRGDSP, was used to dislodge immobilized FN from cell surface integrin receptors.(ABSTRACT TRUNCATED AT 250 WORDS).

  19. Altering the cellular mechanical force balance results in integrated changes in cell, cytoskeletal and nuclear shape

    NASA Technical Reports Server (NTRS)

    Sims, J. R.; Karp, S.; Ingber, D. E.

    1992-01-01

    Studies were carried out with capillary endothelial cells cultured on fibronectin (FN)-coated dishes in order to analyze the mechanism of cell and nuclear shape control by extracellular matrix (ECM). To examine the role of the cytoskeleton in shape determination independent of changes in transmembrane osmotic pressure, membranes of adherent cells were permeabilized with saponin (25 micrograms/ml) using a buffer that maintains the functional integrity of contractile microfilaments. Real-time videomicroscopic studies revealed that addition of 250 microM ATP resulted in time-dependent retraction and rounding of permeabilized cells and nuclei in a manner similar to that observed in intact living cells following detachment using trypsin-EDTA. Computerized image analysis confirmed that permeabilized cells remained essentially rigid in the absence of ATP and that retraction was stimulated in a dose-dependent manner as the concentration of ATP was raised from 10 to 250 microM. Maximal rounding occurred by 30 min with projected cell and nuclear areas being reduced by 69 and 41%, respectively. ATP-induced rounding was also accompanied by a redistribution of microfilaments resulting in formation of a dense net of F-actin surrounding retracted nuclei. Importantly, ATP-stimulated changes in cell, cytoskeletal, and nuclear form were prevented in permeabilized cells using a synthetic myosin peptide (IRICRKG) that has been previously shown to inhibit actomyosin filament sliding in muscle. In contrast, both the rate and extent of cell and nuclear rounding were increased in permeabilized cells exposed to ATP when the soluble FN peptide, GRGDSP, was used to dislodge immobilized FN from cell surface integrin receptors.(ABSTRACT TRUNCATED AT 250 WORDS).

  20. Extreme nuclear shapes examined via giant dipole resonance lineshapes in hot light-mass systems

    SciTech Connect

    Pandit, Deepak; Mukhopadhyay, S.; Pal, Surajit; Bhattacharya, S.; Bhattacharya, C.; Banerjee, K.; Kundu, S.; Rana, T. K.; Dey, A.; Mukherjee, G.; Ghosh, T.; Banerjee, S. R.; De, A.; Gupta, D.

    2010-06-15

    The influence of alpha clustering on nuclear reaction dynamics is investigated using the giant dipole resonance (GDR) lineshape studies in the reactions {sup 20}Ne (E{sub lab}=145,160 MeV) + {sup 12}C and {sup 20}Ne (E{sub lab}=160 MeV) + {sup 27}Al, populating {sup 32}S and {sup 47}V, respectively. The GDR lineshapes from the two systems are remarkably different from each other. Whereas, the non-alpha-like {sup 47}V undergoes Jacobi shape transition and matches exceptionally well with the theoretical GDR lineshape estimated under the framework rotating liquid drop model (RLDM) and thermal shape fluctuation model (TSFM) signifying shape equilibration, for the alpha cluster {sup 32}S an extended prolate kind of shape is observed. This unusual deformation, seen directly via gamma decay for the first time, is predicted to be due to the formation of orbiting dinuclear configuration or molecular structure of {sup 16}O + {sup 16}O in the {sup 32}S superdeformed band.

  1. Nuclear magnetic resonance line shapes of Wigner crystals in 13C-enriched graphene

    NASA Astrophysics Data System (ADS)

    Côté, R.; Parent, Jean-Michel

    2017-06-01

    Assuming that the nuclear magnetic resonance (NMR) signal from a 13C-isotope-enriched layer of graphene can be made sufficiently intense to be measured, we compute the NMR line shape of the different crystals' ground states that are expected to occur in graphene in a strong magnetic field. We first show that in nonuniform states there is, in addition to the frequency shift due to the spin hyperfine interaction, a second contribution of equal importance from the coupling between the orbital motion of the electrons and the nuclei. We then show that if the linewidth of the bare signal can be made sufficiently small, the Wigner and bubble crystals have line shapes that differ qualitatively from that of the uniform state at the same density while crystal states that have spin or valley pseudospin textures do not. Finally, we find that a relatively small value of the bare linewidth is sufficient to wash out the distinctive signature of the crystal states in the NMR line shape.

  2. {alpha} transitions to coexisting 0{sup +} states in Pb and Po isotopes

    SciTech Connect

    Xu Chang; Ren Zhongzhou

    2007-04-15

    The {alpha}-transitions ({delta}l=0) to ground and first excited 0{sup +} states in neutron deficient Pb and Po isotopes are systematically analyzed by the density-dependent cluster model. The magnitude of nuclear deformation of the coexisting 0{sub 1}{sup +} and 0{sub 2}{sup +} states is extracted directly from the experimental {alpha}-decay energies and half-lives. The phenomenon of shape coexistence around the Z=82 shell closure is clearly demonstrated in our present analysis. The obtained deformation values from Rn {yields} Po {yields} Pb decay chains are generally consistent with both the available experimental and theoretical studies.

  3. p63 Transcription Factor Regulates Nuclear Shape and Expression of Nuclear Envelope-Associated Genes in Epidermal Keratinocytes.

    PubMed

    Rapisarda, Valentina; Malashchuk, Igor; Asamaowei, Inemo E; Poterlowicz, Krzysztof; Fessing, Michael Y; Sharov, Andrey A; Karakesisoglou, Iakowos; Botchkarev, Vladimir A; Mardaryev, Andrei

    2017-10-01

    The maintenance of a proper nuclear architecture and three-dimensional organization of the genes, enhancer elements, and transcription machinery plays an essential role in tissue development and regeneration. Here we show that in the developing skin, epidermal progenitor cells of mice lacking p63 transcription factor display alterations in the nuclear shape accompanied by a marked decrease in expression of several nuclear envelope-associated components (Lamin B1, Lamin A/C, Sun1, Nesprin-3, Plectin) compared with controls. Furthermore, chromatin immunoprecipitation-quantitative PCR assay showed enrichment of p63 on Sun1, Syne3, and Plec promoters, suggesting them as p63 targets. Alterations in the nuclei shape and expression of nuclear envelope-associated proteins were accompanied by altered distribution patterns of the repressive histone marks trimethylation on lysine 27 of histone H3, trimethylation on lysine 9 of histone H3, and heterochromatin protein 1-alpha in p63-null keratinocytes. These changes were also accompanied by downregulation of the transcriptional activity and relocation of the keratinocyte-specific gene loci away from the sites of active transcription toward the heterochromatin-enriched repressive nuclear compartments in p63-null cells. These data demonstrate functional links between the nuclear envelope organization, chromatin architecture, and gene expression in keratinocytes and suggest nuclear envelope-associated genes as important targets mediating p63-regulated gene expression program in the epidermis. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  4. Brownian shape motion on five-dimensional potential-energy surfaces:nuclear fission-fragment mass distributions.

    PubMed

    Randrup, Jørgen; Möller, Peter

    2011-04-01

    Although nuclear fission can be understood qualitatively as an evolution of the nuclear shape, a quantitative description has proven to be very elusive. In particular, until now, there existed no model with demonstrated predictive power for the fission-fragment mass yields. Exploiting the expected strongly damped character of nuclear dynamics, we treat the nuclear shape evolution in analogy with Brownian motion and perform random walks on five-dimensional fission potential-energy surfaces which were calculated previously and are the most comprehensive available. Test applications give good reproduction of highly variable experimental mass yields. This novel general approach requires only a single new global parameter, namely, the critical neck size at which the mass split is frozen in, and the results are remarkably insensitive to its specific value.

  5. Brownian Shape Motion on Five-Dimensional Potential-Energy Surfaces:Nuclear Fission-Fragment Mass Distributions

    SciTech Connect

    Randrup, Joergen; Moeller, Peter

    2011-04-01

    Although nuclear fission can be understood qualitatively as an evolution of the nuclear shape, a quantitative description has proven to be very elusive. In particular, until now, there existed no model with demonstrated predictive power for the fission-fragment mass yields. Exploiting the expected strongly damped character of nuclear dynamics, we treat the nuclear shape evolution in analogy with Brownian motion and perform random walks on five-dimensional fission potential-energy surfaces which were calculated previously and are the most comprehensive available. Test applications give good reproduction of highly variable experimental mass yields. This novel general approach requires only a single new global parameter, namely, the critical neck size at which the mass split is frozen in, and the results are remarkably insensitive to its specific value.

  6. Software emulator of nuclear pulse generation with different pulse shapes and pile-up

    NASA Astrophysics Data System (ADS)

    Pechousek, Jiri; Konecny, Daniel; Novak, Petr; Kouril, Lukas; Kohout, Pavel; Celiktas, Cuneyt; Vujtek, Milan

    2016-08-01

    The optimal detection of output signals from nuclear counting devices represents one of the key physical factors that govern accuracy and experimental reproducibility. In this context, the fine calibration of the detector under diverse experimental scenarios, although time costly, is necessary. However this process can be rendered easier with the use of systems that work in lieu of emulators. In this report we describe an innovative programmable pulse generator device capable to emulate the scintillation detector signals, in a way to mimic the detector performances under a variety of experimental conditions. The emulator generates a defined number of pulses, with a given shape and amplitude in the form of a sampled detector signal. The emulator output is then used off-line by a spectrometric system in order to set up its optimal performance. Three types of pulse shapes are produced by our device, with the possibility to add noise and pulse pile-up effects into the signal. The efficiency of the pulse detection, pile-up rejection and/or correction, together with the dead-time of the system, are therein analyzed through the use of some specific algorithms for pulse processing, and the results obtained validate the beneficial use of emulators for the accurate calibration process of spectrometric systems.

  7. Micropatterning of Single Endothelial Cell Shape Reveals a Tight Coupling between Nuclear Volume in G1 and Proliferation

    PubMed Central

    Roca-Cusachs, Pere; Alcaraz, Jordi; Sunyer, Raimon; Samitier, Josep; Farré, Ramon; Navajas, Daniel

    2008-01-01

    Shape-dependent local differentials in cell proliferation are considered to be a major driving mechanism of structuring processes in vivo, such as embryogenesis, wound healing, and angiogenesis. However, the specific biophysical signaling by which changes in cell shape contribute to cell cycle regulation remains poorly understood. Here, we describe our study of the roles of nuclear volume and cytoskeletal mechanics in mediating shape control of proliferation in single endothelial cells. Micropatterned adhesive islands were used to independently control cell spreading and elongation. We show that, irrespective of elongation, nuclear volume and apparent chromatin decondensation of cells in G1 systematically increased with cell spreading and highly correlated with DNA synthesis (percent of cells in the S phase). In contrast, cell elongation dramatically affected the organization of the actin cytoskeleton, markedly reduced both cytoskeletal stiffness (measured dorsally with atomic force microscopy) and contractility (measured ventrally with traction microscopy), and increased mechanical anisotropy, without affecting either DNA synthesis or nuclear volume. Our results reveal that the nuclear volume in G1 is predictive of the proliferative status of single endothelial cells within a population, whereas cell stiffness and contractility are not. These findings show that the effects of cell mechanics in shape control of proliferation are far more complex than a linear or straightforward relationship. Our data are consistent with a mechanism by which spreading of cells in G1 partially enhances proliferation by inducing nuclear swelling and decreasing chromatin condensation, thereby rendering DNA more accessible to the replication machinery. PMID:18326659

  8. Shape coexistence near the N=38 shell gap: Magnetic moment of the 981.6 keV J{sup {pi}=}8{sup +} level in {sup 72}As

    SciTech Connect

    Pantelica, D.; Scintee, N.; Ionescu, P.; Velisa, G.; Negoita, F.; Drafta, G.

    2010-10-15

    We report on the first determination of the magnetic moment of the 981.1 keV, J{sup {pi}=}8{sup +} level in {sup 72}As, a nucleus that belongs to the A{approx_equal}70 mass region dominated by rapidly changing deformations and shapes. The 8{sup +} level is the bandhead of a collective sequence of positive parity levels coexisting with low-spin and medium-spin spherical shell-model states. The magnetic moment was measured by the time-integral perturbed angular distributions method to be {mu}=-(4.272{+-}0.280){mu}{sub N}. This value is in disagreement with the presumed [{pi}(1g{sub 9/2}),{nu}(1g{sub 9/2})] configuration and points to a more complex configuration involving two neutrons in the 1g{sub 9/2} orbital.

  9. RefilinB (FAM101B) targets FilaminA to organize perinuclear actin networks and regulates nuclear shape

    PubMed Central

    Gay, Olivia; Gilquin, Benoît; Nakamura, Fumihiko; Jenkins, Zandra A.; McCartney, Rosannah; Krakow, Deborah; Deshiere, Alexandre; Assard, Nicole; Hartwig, John H.; Robertson, Stephen P.; Baudier, Jacques

    2011-01-01

    The intracellular localization and shape of the nucleus plays a central role in cellular and developmental processes. In fibroblasts, nuclear movement and shape are controlled by a specific perinuclear actin network made of contractile actin filament bundles called transmembrane actin-associated nuclear (TAN) lines that form a structure called the actin cap. The identification of regulatory proteins associated with this specific actin cytoskeletal dynamic is a priority for understanding actin-based changes in nuclear shape and position in normal and pathological situations. Here, we first identify a unique family of actin regulators, the refilin proteins (RefilinA and RefilinB), that stabilize specifically perinuclear actin filament bundles. We next identify the actin-binding filamin A (FLNA) protein as the downstream effector of refilins. Refilins act as molecular switches to convert FLNA from an actin branching protein into one that bundles. In NIH 3T3 fibroblasts, the RefilinB/FLNA complex organizes the perinuclear actin filament bundles forming the actin cap. Finally, we demonstrate that in epithelial normal murine mammary gland (NmuMG) cells, the RefilinB/FLNA complex controls formation of a new perinuclear actin network that accompanies nuclear shape changes during the epithelial–mesenchymal transition (EMT). Our studies open perspectives for further functional analyses of this unique actin-based network and shed light on FLNA function during development and in human syndromes associated with FLNA mutations. PMID:21709252

  10. High resolution microscopy reveals the nuclear shape of budding yeast during cell cycle and in various biological states

    PubMed Central

    Kamgoue, Alain; Normand, Christophe; Léger-Silvestre, Isabelle; Mangeat, Thomas

    2016-01-01

    ABSTRACT How spatial organization of the genome depends on nuclear shape is unknown, mostly because accurate nuclear size and shape measurement is technically challenging. In large cell populations of the yeast Saccharomyces cerevisiae, we assessed the geometry (size and shape) of nuclei in three dimensions with a resolution of 30 nm. We improved an automated fluorescence localization method by implementing a post-acquisition correction of the spherical microscopic aberration along the z-axis, to detect the three dimensional (3D) positions of nuclear pore complexes (NPCs) in the nuclear envelope. Here, we used a method called NucQuant to accurately estimate the geometry of nuclei in 3D throughout the cell cycle. To increase the robustness of the statistics, we aggregated thousands of detected NPCs from a cell population in a single representation using the nucleolus or the spindle pole body (SPB) as references to align nuclei along the same axis. We could detect asymmetric changes of the nucleus associated with modification of nucleolar size. Stereotypical modification of the nucleus toward the nucleolus further confirmed the asymmetric properties of the nuclear envelope. PMID:27831493

  11. High resolution microscopy reveals the nuclear shape of budding yeast during cell cycle and in various biological states.

    PubMed

    Wang, Renjie; Kamgoue, Alain; Normand, Christophe; Léger-Silvestre, Isabelle; Mangeat, Thomas; Gadal, Olivier

    2016-12-15

    How spatial organization of the genome depends on nuclear shape is unknown, mostly because accurate nuclear size and shape measurement is technically challenging. In large cell populations of the yeast Saccharomyces cerevisiae, we assessed the geometry (size and shape) of nuclei in three dimensions with a resolution of 30 nm. We improved an automated fluorescence localization method by implementing a post-acquisition correction of the spherical microscopic aberration along the z-axis, to detect the three dimensional (3D) positions of nuclear pore complexes (NPCs) in the nuclear envelope. Here, we used a method called NucQuant to accurately estimate the geometry of nuclei in 3D throughout the cell cycle. To increase the robustness of the statistics, we aggregated thousands of detected NPCs from a cell population in a single representation using the nucleolus or the spindle pole body (SPB) as references to align nuclei along the same axis. We could detect asymmetric changes of the nucleus associated with modification of nucleolar size. Stereotypical modification of the nucleus toward the nucleolus further confirmed the asymmetric properties of the nuclear envelope. © 2016. Published by The Company of Biologists Ltd.

  12. Nuclear Data Library Effects on Fast to Thermal Flux Shapes Around PWR Control Rod Tips

    NASA Astrophysics Data System (ADS)

    Vasiliev, A.; Ferroukhi, H.; Zhu, T.; Pautz, A.

    2014-04-01

    The development of a high-fidelity computational scheme to estimate the accumulated fluence at the tips of PWR control rods (CR) has been initiated at the Paul Scherrer Institut (PSI). Both the fluence from high-energy (E>1 MeV) neutrons as well as for the thermal range (E<0.625 eV) are required as these affect the CR integrity through stresses/strains induced by coupled clad embrittlement / absorber swelling phenomena. The concept of the PSI scheme under development is to provide from validated core analysis models, the volumetric neutron source to a full core MCNPX model that is then used to compute the neutron fluxes. A particular aspect that needs scrutiny is the ability of the MCNPX-based calculation methodology to accurately predict the flux shapes along the control rod surfaces, especially for fully withdrawn CRs. In that case, the tip is located a short distance above the core/reflector interface and since this situation corresponds to a large part of reactor operation, the accumulated fluence will highly depend on the achieved calculation accuracy and precision in this non-fueled zone. The objective of the work presented in this paper is to quantify the influence of nuclear data on the calculated fluxes at the CR tips by (1) conducting a systematic comparison of modern neutron cross-section libraries, including JENDL-4.0, JEFF-3.1.1 and ENDF/B-VII.0, and (2) by quantifying the uncertainties in the neutron flux calculations with the help of available neutron cross-section variances/covariances data. For completeness, the magnitude of these nuclear data-based uncertainties is also assessed in relation to the influence from other typical sources of modeling uncertainties/biases.

  13. Three-Dimensional Analysis of Nuclear Size, Shape and Displacement in Clover Root Cap Statocytes from Space and a Clinostat

    NASA Technical Reports Server (NTRS)

    Smith, J.D.; Todd, P. W.; Staehelin, L. A.; Holton, Emily (Technical Monitor)

    1997-01-01

    Under normal (l-g) conditions the statocytes of root caps have a characteristic polarity with the nucleus in tight association with the proximal cell wall; but, in altered gravity environments including microgravity (mu-g) and the clinostat (c-g) movement of the nucleus away from the proximal cell wall is not uncommon. To further understand the cause of gravity-dependent nuclear displacement in statocytes, three-dimensional cell reconstruction techniques were used to precisely measure the volumes, shapes, and positions of nuclei in white clover (Trifolium repens) flown in space and rotated on a clinostat. Seeds were germinated and grown for 72 hours aboard the Space Shuttle (STS-63) in the Fluid Processing Apparatus (BioServe Space Technologies, Univ. of Colorado, Boulder). Clinorotation experiments were performed on a two-axis clinostat (BioServe). Computer reconstruction of selected groups of statocytes were made from serial sections (0.5 microns thick) using the ROSS (Reconstruction Of Serial Sections) software package (Biocomputation Center, NASA Ames Research Center). Nuclei were significantly displaced from the tops of cells in mu-g (4.2 +/- 1.0 microns) and c-g (4.9 +/- 1.4 microns) when compared to l-g controls (3.4 +/- 0.8 gm); but, nuclear volume (113 +/- 36 cu microns, 127 +/- 32 cu microns and 125 +/- 28 cu microns for l-g, mu-g and c-g respectively) and the ratio of nuclear volume to cell volume (4.310.7%, 4.211.0% and 4.911.4% respectively) were not significantly dependent on gravity treatment (ANOVA; alpha = 0.05). Three-dimensional analysis of nuclear shape and proximity to the cell wall, however, showed that nuclei from l-g controls appeared ellipsoidal while those from space and the clinostat were more spherically shaped. This change in nuclear shape may be responsible for its displacement under altered gravity conditions. Since the cytoskeleton is known to affect nuclear polarity in root cap statocytes, those same cytoskeletal elements could also

  14. Three-Dimensional Analysis of Nuclear Size, Shape and Displacement in Clover Root Cap Statocytes from Space and a Clinostat

    NASA Technical Reports Server (NTRS)

    Smith, J.D.; Todd, P. W.; Staehelin, L. A.; Holton, Emily (Technical Monitor)

    1997-01-01

    Under normal (l-g) conditions the statocytes of root caps have a characteristic polarity with the nucleus in tight association with the proximal cell wall; but, in altered gravity environments including microgravity (mu-g) and the clinostat (c-g) movement of the nucleus away from the proximal cell wall is not uncommon. To further understand the cause of gravity-dependent nuclear displacement in statocytes, three-dimensional cell reconstruction techniques were used to precisely measure the volumes, shapes, and positions of nuclei in white clover (Trifolium repens) flown in space and rotated on a clinostat. Seeds were germinated and grown for 72 hours aboard the Space Shuttle (STS-63) in the Fluid Processing Apparatus (BioServe Space Technologies, Univ. of Colorado, Boulder). Clinorotation experiments were performed on a two-axis clinostat (BioServe). Computer reconstruction of selected groups of statocytes were made from serial sections (0.5 microns thick) using the ROSS (Reconstruction Of Serial Sections) software package (Biocomputation Center, NASA Ames Research Center). Nuclei were significantly displaced from the tops of cells in mu-g (4.2 +/- 1.0 microns) and c-g (4.9 +/- 1.4 microns) when compared to l-g controls (3.4 +/- 0.8 gm); but, nuclear volume (113 +/- 36 cu microns, 127 +/- 32 cu microns and 125 +/- 28 cu microns for l-g, mu-g and c-g respectively) and the ratio of nuclear volume to cell volume (4.310.7%, 4.211.0% and 4.911.4% respectively) were not significantly dependent on gravity treatment (ANOVA; alpha = 0.05). Three-dimensional analysis of nuclear shape and proximity to the cell wall, however, showed that nuclei from l-g controls appeared ellipsoidal while those from space and the clinostat were more spherically shaped. This change in nuclear shape may be responsible for its displacement under altered gravity conditions. Since the cytoskeleton is known to affect nuclear polarity in root cap statocytes, those same cytoskeletal elements could also

  15. Nuclear Shape Changes Are Induced by Knockdown of the SWI/SNF ATPase BRG1 and Are Independent of Cytoskeletal Connections

    PubMed Central

    Imbalzano, Karen M.; Cohet, Nathalie; Wu, Qiong; Underwood, Jean M.; Imbalzano, Anthony N.; Nickerson, Jeffrey A.

    2013-01-01

    Changes in nuclear morphology occur during normal development and have been observed during the progression of several diseases. The shape of a nucleus is governed by the balance of forces exerted by nuclear-cytoskeletal contacts and internal forces created by the structure of the chromatin and nuclear envelope. However, factors that regulate the balance of these forces and determine nuclear shape are poorly understood. The SWI/SNF chromatin remodeling enzyme ATPase, BRG1, has been shown to contribute to the regulation of overall cell size and shape. Here we document that immortalized mammary epithelial cells show BRG1-dependent nuclear shape changes. Specifically, knockdown of BRG1 induced grooves in the nuclear periphery that could be documented by cytological and ultrastructural methods. To test the hypothesis that the observed changes in nuclear morphology resulted from altered tension exerted by the cytoskeleton, we disrupted the major cytoskeletal networks and quantified the frequency of BRG1-dependent changes in nuclear morphology. The results demonstrated that disruption of cytoskeletal networks did not change the frequency of BRG1-induced nuclear shape changes. These findings suggest that BRG1 mediates control of nuclear shape by internal nuclear mechanisms that likely control chromatin dynamics. PMID:23405182

  16. Pulse-shape discrimination between electron and nuclear recoils in a NaI(Tl) crystal

    NASA Astrophysics Data System (ADS)

    Lee, H. S.; Adhikari, G.; Adhikari, P.; Choi, S.; Hahn, I. S.; Jeon, E. J.; Joo, H. W.; Kang, W. G.; Kim, G. B.; Kim, H. J.; Kim, H. O.; Kim, K. W.; Kim, N. Y.; Kim, S. K.; Kim, Y. D.; Kim, Y. H.; Lee, J. H.; Lee, M. H.; Leonard, D. S.; Li, J.; Oh, S. Y.; Olsen, S. L.; Park, H. K.; Park, H. S.; Park, K. S.; Shim, J. H.; So, J. H.

    2015-08-01

    We report on the response of a high light-output NaI(Tl) crystal to nuclear recoils induced by neutrons from an Am-Be source and compare the results with the response to electron recoils produced by Compton-scattered 662 keV γ-rays from a 137Cs source. The measured pulse-shape discrimination (PSD) power of the NaI(Tl) crystal is found to be significantly improved because of the high light output of the NaI(Tl) detector. We quantify the PSD power with a quality factor and estimate the sensitivity to the interaction rate for weakly interacting massive particles (WIMPs) with nucleons, and the result is compared with the annual modulation amplitude observed by the DAMA/LIBRA experiment. The sensitivity to spin-independent WIMP-nucleon interactions based on 100 kg·year of data from NaI detectors is estimated with simulated experiments, using the standard halo model.

  17. Global analysis of quadrupole shape invariants based on covariant energy density functionals

    NASA Astrophysics Data System (ADS)

    Quan, S.; Chen, Q.; Li, Z. P.; Nikšić, T.; Vretenar, D.

    2017-05-01

    Background: The coexistence of different geometric shapes at low energies presents a universal structure phenomenon that occurs over the entire chart of nuclides. Studies of the shape coexistence are important for understanding the microscopic origin of collectivity and modifications of shell structure in exotic nuclei far from stability. Purpose: The aim of this work is to provide a systematic analysis of characteristic signatures of coexisting nuclear shapes in different mass regions, using a global self-consistent theoretical method based on universal energy density functionals and the quadrupole collective model. Method: The low-energy excitation spectrum and quadrupole shape invariants of the two lowest 0+ states of even-even nuclei are obtained as solutions of a five-dimensional collective Hamiltonian (5DCH) model, with parameters determined by constrained self-consistent mean-field calculations based on the relativistic energy density functional PC-PK1, and a finite-range pairing interaction. Results: The theoretical excitation energies of the states, 21+,41+,02+,22+,23+, as well as the B (E 2 ;01+→21+) values, are in very good agreement with the corresponding experimental values for 621 even-even nuclei. Quadrupole shape invariants have been implemented to investigate shape coexistence, and the distribution of possible shape-coexisting nuclei is consistent with results obtained in recent theoretical studies and available data. Conclusions: The present analysis has shown that, when based on a universal and consistent microscopic framework of nuclear density functionals, shape invariants provide distinct indicators and reliable predictions for the occurrence of low-energy coexisting shapes. This method is particularly useful for studies of shape coexistence in regions far from stability where few data are available.

  18. Nuclear shape and structure in neutron-rich {sup 110,111}Tc

    SciTech Connect

    Luo, Y. X.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Gore, P. M.; Jones, E. F.; Fong, D.; Rasmussen, J. O.; Lee, I. Y.; Stefanescu, I.; Che, X. L.; Zhu, S. J.; Wu, S. C.; Ginter, T. N.; Ma, W. C.; Ter-Akopian, G. M.; Daniel, A. V.; Stoyer, M. A.; Donangelo, R.; Gelberg, A.

    2006-08-15

    The high-spin nuclear structure of Tc isotopes is extended to more neutron-rich regions based on the measurements of prompt {gamma} rays from the spontaneous fission of {sup 252}Cf at the Gammasphere. The high-spin level scheme of N=67 neutron-rich {sup 110}Tc (Z=43) is established for the first time, and that of {sup 111}Tc is extended and expanded. The ground band of {sup 111}Tc reaches the band-crossing region, and the new observation of the weakly populated {alpha}=-1/2 member of the band provides important information on signature splitting. The systematics of band crossings in the isotopic and isotonic chains and a CSM calculation suggest that the band crossing of the ground band of {sup 111}Tc is due to alignment of a pair of h{sub 11/2} neutrons. The best fit to signature splitting, branching ratios, and excitations of the ground band of {sup 111}Tc by the rigid triaxial rotor plus particle model calculations result in a shape of {epsilon}{sub 2}=0.32 and {gamma}=-26 deg. for this nucleus. Its triaxiality is larger than that of {sup 107,109}Tc, which indicates increasing triaxiality in Tc isotopes with increasing neutron number. The identification of the weakly populated K+2 satellite band provides strong evidence for the large triaxiality of {sup 111}Tc. In {sup 110}Tc, the four lowest-lying levels observed are very similar to those in {sup 108}Tc. At an excitation of 478.9 keV above the lowest state observed, ten states of a {delta}I=1 band are observed. This band of {sup 110}Tc is very analogous to the {delta}I=1 bands in {sup 106,108}Tc, but it has greater and reversal signature splitting at higher spins.

  19. Decay of mass-separated 3.0 min 195gBi to levels in 195Pb and shape coexistence in the neutron-deficient odd-mass Pb isotopes

    NASA Astrophysics Data System (ADS)

    Griffin, J. C.; Braga, R. A.; Fink, R. W.; Wood, J. L.; Carter, H. K.; Mlekodaj, R. L.; Bingham, C. R.; Coenen, E.; Huyse, M.; Van Duppen, P.

    1991-08-01

    The radioactive decay of mass-separated 3.0 m 195gBi to 195Pb has been studied with the UNISOR and LISOL facilities. Time-sequenced spectra of γ-rays, X-rays, and conversion electrons have been obtained, together with γγt, γXt, eγt, and eXt coincidence data. From this information, a decay scheme has been constructed consisting of 23 excited states and 34 transitions in 195Pb. Transitions with E0 multipole admixtures, indicative of shape coexistence, have been found to de-excite positive-parity levels at 1093, 1329, and 1380 keV. The beta-decay energy of the 195Bi ground state is deduced to be QEC = 4800 -550+600 keV based on the measurement of γ-ray-gated K/ β+ ratios. The excitation energy of the i{13}/{2} isomer in 195Pb has been determined to be 203±4 keV from the α-decays of 199m,gPo.

  20. Role of Actin Filaments in Correlating Nuclear Shape and Cell Spreading

    PubMed Central

    Vishavkarma, Renu; Raghavan, Swetavalli; Kuyyamudi, Chandrashekar; Majumder, Abhijit; Dhawan, Jyotsna; Pullarkat, Pramod A.

    2014-01-01

    It is well known that substrate properties like stiffness and adhesivity influence stem cell morphology and differentiation. Recent experiments show that cell morphology influences nuclear geometry and hence gene expression profile. The mechanism by which surface properties regulate cell and nuclear properties is only beginning to be understood. Direct transmission of forces as well as chemical signalling are involved in this process. Here, we investigate the formal aspect by studying the correlation between cell spreading and nuclear deformation using Mesenchymal stem cells under a wide variety of conditions. It is observed that a robust quantitative relation holds between the cell and nuclear projected areas, irrespective of how the cell area is modified or when various cytoskeletal or nuclear components are perturbed. By studying the role of actin stress fibers in compressing the nucleus we propose that nuclear compression by stress fibers can lead to enhanced cell spreading due to an interplay between elastic and adhesion factors. The significance of myosin-II in regulating this process is also explored. We demonstrate this effect using a simple technique to apply external compressive loads on the nucleus. PMID:25251154

  1. Novel plant SUN-KASH bridges are involved in RanGAP anchoring and nuclear shape determination.

    PubMed

    Zhou, Xiao; Graumann, Katja; Evans, David E; Meier, Iris

    2012-01-23

    Inner nuclear membrane Sad1/UNC-84 (SUN) proteins interact with outer nuclear membrane (ONM) Klarsicht/ANC-1/Syne homology (KASH) proteins, forming linkers of nucleoskeleton to cytoskeleton conserved from yeast to human and involved in positioning of nuclei and chromosomes. Defects in SUN-KASH bridges are linked to muscular dystrophy, progeria, and cancer. SUN proteins were recently identified in plants, but their ONM KASH partners are unknown. Arabidopsis WPP domain-interacting proteins (AtWIPs) are plant-specific ONM proteins that redundantly anchor Arabidopsis RanGTPase-activating protein 1 (AtRanGAP1) to the nuclear envelope (NE). In this paper, we report that AtWIPs are plant-specific KASH proteins interacting with Arabidopsis SUN proteins (AtSUNs). The interaction is required for both AtWIP1 and AtRanGAP1 NE localization. AtWIPs and AtSUNs are necessary for maintaining the elongated nuclear shape of Arabidopsis epidermal cells. Together, our data identify the first KASH members in the plant kingdom and provide a novel function of SUN-KASH complexes, suggesting that a functionally diverged SUN-KASH bridge is conserved beyond the opisthokonts.

  2. gA-driven shapes of electron spectra of forbidden β decays in the nuclear shell model

    NASA Astrophysics Data System (ADS)

    Kostensalo, Joel; Suhonen, Jouni

    2017-08-01

    The evolution of the shape of the electron spectra of 16 forbidden β- decays as a function of gA was studied using the nuclear shell model in appropriate single-particle model spaces with established, well-tested nuclear Hamiltonians. The β spectra of 94Nb(6+) →94Mo(4+) and 98Tc(6+) →98Ru(4+) were found to depend strongly on gA, which makes them excellent candidates for the determination of the effective value of gA with the spectrum-shape method (SSM). A strong gA dependence is also seen in the spectrum of 96Zr(0+) →96Nb(6+) . This decay could be used for determining the quenching of gA in sixth-forbidden decays in the future, when the measurement of the spectrum becomes experimentally feasible. The calculated shell-model electron spectra of the ground-state-to-ground-state decays of 87Rb, 99Tc, and 137Cs and the decay of 137Cs to the isomeric 11 /2- state in 137Ba were found to be in excellent agreement with the spectra previously calculated using the microscopic quasiparticle-phonon model. This is further evidence of the robust nature of the SSM observed in the previous studies.

  3. Geometry of coexistence in the interacting boson model

    SciTech Connect

    Van Isacker, P.; Frank, A.; Vargas, C.E.

    2004-09-13

    The Interacting Boson Model (IBM) with configuration mixing is applied to describe the phenomenon of coexistence in nuclei. The analysis suggests that the IBM with configuration mixing, used in conjunction with a (matrix) coherent-state method, may be a reliable tool for the study of geometric aspects of shape coexistence in nuclei.

  4. Nuclear shape transitions and some properties of aligned-particle configurations at high spin

    SciTech Connect

    Koo, T.L.; Chowdhury, P.; Emling, H.

    1982-01-01

    Two topics are addressed in this paper. First, we discuss the variation of shapes with spin and neutron number for nuclei in the N approx. = 88 transitional region. Second, we present comments on the feeding times of very high spin single-particle yrast states.

  5. Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon

    SciTech Connect

    Cao, H.

    2015-05-26

    We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We also report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0 to 970 V/cm. For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V/cm. Furthermore, we report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from 83mKr internal conversion electrons is comparable to that from 207Bi conversion electrons, we obtained the numbers of excitons (Nex) and ion pairs (Ni) and their ratio (Nex/Ni) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.

  6. Measurement of scintillation and ionization yield and scintillation pulse shape from nuclear recoils in liquid argon

    NASA Astrophysics Data System (ADS)

    Cao, H.; Alexander, T.; Aprahamian, A.; Avetisyan, R.; Back, H. O.; Cocco, A. G.; Dejongh, F.; Fiorillo, G.; Galbiati, C.; Grandi, L.; Guardincerri, Y.; Kendziora, C.; Lippincott, W. H.; Love, C.; Lyons, S.; Manenti, L.; Martoff, C. J.; Meng, Y.; Montanari, D.; Mosteiro, P.; Olvitt, D.; Pordes, S.; Qian, H.; Rossi, B.; Saldanha, R.; Sangiorgio, S.; Siegl, K.; Strauss, S. Y.; Tan, W.; Tatarowicz, J.; Walker, S.; Wang, H.; Watson, A. W.; Westerdale, S.; Yoo, J.; Scene Collaboration

    2015-05-01

    We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0 to 970 V /cm . For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V /cm . We also report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from Krm83 internal conversion electrons is comparable to that from 207Bi conversion electrons, we obtained the numbers of excitons (Nex) and ion pairs (Ni) and their ratio (Nex/Ni ) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.

  7. Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon

    DOE PAGES

    Cao, H.

    2015-05-26

    We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We also report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0more » to 970 V/cm. For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V/cm. Furthermore, we report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from 83mKr internal conversion electrons is comparable to that from 207Bi conversion electrons, we obtained the numbers of excitons (Nex) and ion pairs (Ni) and their ratio (Nex/Ni) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.« less

  8. Measurement of scintillation and ionization yield and scintillation pulse shape from nuclear recoils in liquid argon

    SciTech Connect

    Cao, H.; Alexander, T.; Aprahamian, A.; Avetisyan, R.; Back, H. O.; Cocco, A. G.; DeJongh, F.; Fiorillo, G.; Galbiati, C.; Grandi, L.; Guardincerri, Y.; Kendziora, C.; Lippincott, W. H.; Love, C.; Lyons, S.; Manenti, L.; Martoff, C. J.; Meng, Y.; Montanari, D.; Mosteiro, P.; Olvitt, D.; Pordes, S.; Qian, H.; Rossi, B.; Saldanha, R.; Sangiorgio, S.; Siegl, K.; Strauss, S. Y.; Tan, W.; Tatarowicz, J.; Walker, S.; Wang, H.; Watson, A. W.; Westerdale, S.; Yoo, J.

    2015-05-01

    We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0 to 970 V / cm . For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V / cm . We also report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from 83 m Kr internal conversion electrons is comparable to that from 207 Bi conversion electrons, we obtained the numbers of excitons ( N ex ) and ion pairs ( N i ) and their ratio ( N ex / N i ) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.

  9. Hutchinson-Gilford progeria syndrome alters nuclear shape and reduces cell motility in three dimensional model substrates.

    PubMed

    Booth-Gauthier, Elizabeth A; Du, Vicard; Ghibaudo, Marion; Rape, Andrew D; Dahl, Kris Noel; Ladoux, Benoit

    2013-03-01

    Cell migration through tight interstitial spaces in three dimensional (3D) environments impacts development, wound healing and cancer metastasis and is altered by the aging process. The stiffness of the extracellular matrix (ECM) increases with aging and affects the cells and cytoskeletal processes involved in cell migration. However, the nucleus, which is the largest and densest organelle, has not been widely studied during cell migration through the ECM. Additionally, the nucleus is stiffened during the aging process through the accumulation of a mutant nucleoskeleton protein lamin A, progerin. By using microfabricated substrates to mimic the confined environment of surrounding tissues, we characterized nuclear movements and deformation during cell migration into micropillars where interspacing can be tuned to vary nuclear confinement. Cell motility decreased with decreased micropillar (μP) spacing and correlated with increased dysmorphic shapes of nuclei. We examined the effects of increased nuclear stiffness which correlates with cellular aging by studying Hutchinson-Gilford progeria syndrome cells which are known to accumulate progerin. With the expression of progerin, cells showed a threshold response to decreased μP spacing. Cells became trapped in the close spacing, possibly from visible micro-defects in the nucleoskeleton induced by cell crawling through the μP and from reduced force generation, measured independently. We suggest that ECM changes during aging could be compounded by the increasing stiffness of the nucleus and thus changes in cell migration through 3D tissues.

  10. Triple configuration coexistence in {sup 44}S

    SciTech Connect

    Santiago-Gonzalez, D.; Wiedenhoever, I.; Abramkina, V.; Avila, M. L.; Cottle, P. D.; Kemper, K. W.; Rojas, A.; Volya, A.; Baugher, T.; Brown, B. A.; Gade, A.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Meharchand, R.; Bazin, D.; Weisshaar, D.; Simpson, E. C.; Tostevin, J. A.

    2011-06-15

    The neutron-rich N=28 nucleus {sup 44}S was studied using the two-proton knockout reaction from {sup 46}Ar at intermediate beam energy. We report the observation of four new excited states, one of which is a strongly prolate deformed 4{sup +} state, as indicated by a shell-model calculation. Its deformation originates in a neutron configuration which is fundamentally different from the ''intruder'' configuration responsible for the ground-state deformation. Consequently, we do not have three coexisting shapes in {sup 44}S, but three coexisting configurations, corresponding to zero-, one-, and two-neutron particle-hole excitations.

  11. Frequent chloroplast RNA editing in early-branching flowering plants: pilot studies on angiosperm-wide coexistence of editing sites and their nuclear specificity factors.

    PubMed

    Hein, Anke; Polsakiewicz, Monika; Knoop, Volker

    2016-01-25

    RNA editing by cytidine-to-uridine conversions is an essential step of RNA maturation in plant organelles. Some 30-50 sites of C-to-U RNA editing exist in chloroplasts of flowering plant models like Arabidopsis, rice or tobacco. We now predicted significantly more RNA editing in chloroplasts of early-branching angiosperm genera like Amborella, Calycanthus, Ceratophyllum, Chloranthus, Illicium, Liriodendron, Magnolia, Nuphar and Zingiber. Nuclear-encoded RNA-binding pentatricopeptide repeat (PPR) proteins are key editing factors expected to coevolve with their cognate RNA editing sites in the organelles. With an extensive chloroplast transcriptome study we identified 138 sites of RNA editing in Amborella trichopoda, approximately the 3- to 4-fold of cp editing in Arabidopsis thaliana or Oryza sativa. Selected cDNA studies in the other early-branching flowering plant taxa furthermore reveal a high diversity of early angiosperm RNA editomes. Many of the now identified editing sites in Amborella have orthologues in ferns, lycophytes or hornworts. We investigated the evolution of CRR28 and RARE1, two known Arabidopsis RNA editing factors responsible for cp editing events ndhBeU467PL, ndhDeU878SL and accDeU794SL, respectively, all of which we now found conserved in Amborella. In a phylogenetically wide sampling of 65 angiosperm genomes we find evidence for only one single loss of CRR28 in chickpea but several independent losses of RARE1, perfectly congruent with the presence of their cognate editing sites in the respective cpDNAs. Chloroplast RNA editing is much more abundant in early-branching than in widely investigated model flowering plants. RNA editing specificity factors can be traced back for more than 120 million years of angiosperm evolution and show highly divergent patterns of evolutionary losses, matching the presence of their target editing events.

  12. Effective bilayer expansion and erythrocyte shape change induced by monopalmitoyl phosphatidylcholine. Quantitative light microscopy and nuclear magnetic resonance spectroscopy measurements.

    PubMed Central

    Chi, L M; Wu, W G

    1990-01-01

    When human erythrocytes are treated with exogenous monopalmitoyl phosphatidylcholine (MPPC), the normal biconcave disk shape red blood cells (RBC) become spiculate echinocytes. The present study examines the quantitative aspect of the relationship between effective bilayer expansion and erythrocyte shape change by a newly developed method. This method is based on the combination of direct surface area measurement of micropipette and relative bilayer expansion measurement of 13C crosspolarization/magic angle spinning nuclear magnetic resonance (NMR). Assuming that 13C NMR chemical shift of fatty acyl chain can be used as an indicator of lateral packing of membrane bilayers, it is possible for us to estimate the surface area expansion of red cell membrane induced by MPPC from that induced by ethanol. Partitions of lipid molecules into cell membrane were determined by studies of shape change potency as a function of MPPC and red cell concentration. It is found that 8(+/- 0.5) x 10(6) molecules of MPPC per cell will effectively induce stage three echinocytes and yield 3.2(+/- 0.2)% expansion of outer monolayer surface area. Surface area of normal cells determined by direct measurements from fixed geometry of red cells aspirated by micropipette was 118.7 +/- 8.5 microns2. The effective cross-sectional area of MPPC molecules in the cell membrane therefore was determined to be 48(+/- 4) A2, which is in agreement with those determined by x-ray from model membranes and crystals of lysophospholipids. We concluded that surface area expansion of RBC can be explained by a simple consideration of cross-sectional area of added molecules and that erythrocyte shape changes correspond quantitatively to the incorporated lipid molecules. Images FIGURE 3 PMID:2393706

  13. Ephemeral Protein Binding to DNA Shapes Stable Nuclear Bodies and Chromatin Domains.

    PubMed

    Brackley, Chris A; Liebchen, Benno; Michieletto, Davide; Mouvet, Francois; Cook, Peter R; Marenduzzo, Davide

    2017-03-28

    Fluorescence microscopy reveals that the contents of many (membrane-free) nuclear bodies exchange rapidly with the soluble pool while the underlying structure persists; such observations await a satisfactory biophysical explanation. To shed light on this, we perform large-scale Brownian dynamics simulations of a chromatin fiber interacting with an ensemble of (multivalent) DNA-binding proteins able to switch between an "on" (binding) and an "off" (nonbinding) state. This system provides a model for any DNA-binding protein that can be posttranslationally modified to change its affinity for DNA (e.g., through phosphorylation). Protein switching is a nonequilibrium process, and it leads to the formation of clusters of self-limiting size, where individual proteins in a cluster exchange with the soluble pool with kinetics similar to those seen in photobleaching experiments. This behavior contrasts sharply with that exhibited by nonswitching proteins, which are permanently in the on-state; when these bind to DNA nonspecifically, they form clusters that grow indefinitely in size. To explain these findings, we propose a mean-field theory from which we obtain a scaling relation between the typical cluster size and the protein switching rate. Protein switching also reshapes intrachromatin contacts to give networks resembling those seen in topologically associating domains, as switching markedly favors local (short-range) contacts over distant ones. Our results point to posttranslational modification of chromatin-bridging proteins as a generic mechanism driving the self-assembly of highly dynamic, nonequilibrium, protein clusters with the properties of nuclear bodies.

  14. Shape change and shape coexistence in134Pr

    NASA Astrophysics Data System (ADS)

    Petrache, C. M.; de Angelis, G.; Bucurescu, D.; Ivascu, M.; Bazzacco, D.; Lunardi, S.

    1992-06-01

    The band structure of doubly odd nucleus134Pr has been studied by means of the reaction119Sn(19F,4n) at 87 MeV bombarding energy. Rotational bands built on πh11/2⊗vh11/2 and πh7/2⊗vh11/2 configurations has been observed. A band consisting of quadrupole transitions, probably involving the vi13/2[600]1/2+ orbital was also weakly populated.

  15. Pump-shaped dump optimal control reveals the nuclear reaction pathway of isomerization of a photoexcited cyanine dye.

    PubMed

    Dietzek, Benjamin; Brüggemann, Ben; Pascher, Torbjörn; Yartsev, Arkady

    2007-10-31

    Using optimal control as a spectroscopic tool we decipher the details of the molecular dynamics of the essential multidimensional excited-state photoisomerization - a fundamental chemical reaction of key importance in biology. Two distinct nuclear motions are identified in addition to the overall bond-twisting motion: Initially, the reaction is dominated by motion perpendicular to the torsion coordinate. At later times, a second optically active vibration drives the system along the reaction path to the bottom of the excited-state potential. The time scales of the wavepacket motion on a different part of the excited-state potential are detailed by pump-shaped dump optimal control. This technique offers new means to control a chemical reaction far from the Franck-Condon point of absorption and to map details of excited-state reaction pathways revealing unique insights into the underlying reaction mechanism.

  16. Evolution of nuclear shapes in odd-mass yttrium and niobium isotopes from lifetime measurements following fission reactions

    NASA Astrophysics Data System (ADS)

    Hagen, T. W.; Görgen, A.; Korten, W.; Grente, L.; Salsac, M.-D.; Farget, F.; Ragnarsson, I.; Braunroth, T.; Bruyneel, B.; Celikovic, I.; Clément, E.; de France, G.; Delaune, O.; Dewald, A.; Dijon, A.; Hackstein, M.; Jacquot, B.; Litzinger, J.; Ljungvall, J.; Louchart, C.; Michelagnoli, C.; Napoli, D. R.; Recchia, F.; Rother, W.; Sahin, E.; Siem, S.; Sulignano, B.; Theisen, Ch.; Valiente-Dobon, J. J.

    2017-03-01

    Lifetimes of excited states in 99Y,101Y,101Nb,103Nb, and 105Nb were measured in an experiment using the recoil distance Doppler shift method at GANIL (Grand Accélérateur National d'Ions Lourds). The neutron-rich nuclei were produced in fission reactions between a 238U beam and a 9Be target. Prompt γ rays were measured with the EXOGAM array and correlated with fission fragments that were identified in mass and atomic number with the VAMOS++ spectrometer. The measured lifetimes, together with branching ratios, provide B (M 1 ) and B (E 2 ) values for the strongly coupled rotational bands built on the [422 ] 5 /2+ ground state in the Y and Nb nuclei with neutron number N ≥60 . The comparison of the experimental results with triaxial particle-rotor calculations provides information about the evolution of the nuclear shape in this mass region.

  17. Using an Inertial Electrostatic Confinement (IEC) Nuclear Fusion Device as a Pulsed Neutron Source: Optimizing the Pulse Shape

    NASA Astrophysics Data System (ADS)

    Bonomo, Richard

    2010-11-01

    Pulsed neutron sources may prove to be valuable for detecting illicit nuclear materials in items being smuggled across borders or checkpoints. Work already accomplished by Sorebo et al. [1] at the U. of Wisconsin demonstrated the basic detection concept by successfully detecting delayed ^235U fission neutrons using neutron pulses generated by an IEC fusion device. Numerical studies imply the detection of the much more copious prompt induced-fission neutrons would be preferable; the experimental detection of prompt neutrons represents a challenge: the prompt, fission-produced neutron and interrogating neutron pulses may overlap. After IEC device operation and past work by Sorebo et al. are reviewed, efforts to produce a properly shaped interrogating neutron pulse are described. Efforts drawing, in part, on techniques used in hard-switched power inverters are highlighted.[4pt] [1] J.H. Sorebo, G.L. Kulcinski, R.F. Radel, and J.F. Santarius, ``Special Nuclear Materials Detection Using IEC Fusion Pulsed Neutron Source,'' Fusion Science and Technology 56, 540 (2009).

  18. Probing nuclear shapes close to the fission limit with the giant dipole resonance in {sup 216}Rn

    SciTech Connect

    Kmiecik, M.; Maj, A.; Brekiesz, M.; Krolas, W.; Meczynski, W.; Styczen, J.; Zieblinski, M.; Million, B.; Bracco, A.; Camera, F.; Benzoni, G.; Leoni, S.; Wieland, O.; Brambilla, S.; Herskind, B.; Kicinska-Habior, M.; Dubray, N.; Dudek, J.; Schunck, N.

    2004-12-01

    The gamma-ray decay of the giant dipole resonance (GDR) in the compound nucleus {sup 216}Rn formed with the reaction {sup 18}O+{sup 198}Pt at the bombarding energy of 96 MeV was investigated. High-energy gamma-ray spectra in coincidence with both prompt and delayed low-energy transitions were measured. The obtained GDR width at the average temperature {approx_equal}1 MeV was found to be larger than that at T=0 MeV and to be approximately constant as a function of spin. The measured width value of 7 MeV is found to be consistent with the predictions based on calculations of the nuclear shape distribution using the newest approach for the treatment of the fission barrier within the liquid drop model. The present study is the first investigation of the giant dipole resonance width from the fusion-evaporation decay channel in this nuclear mass range.

  19. [Alveolar bone loss in nuclear families of aggressive periodontitis and the heredity of root shape].

    PubMed

    Qiao, Min; Xu, Li; Meng, Huan-xin; Tian, Yu; Zhang, Li; Feng, Xiang-hui

    2013-10-01

    To evaluate the status of residual alveolar bone in aggressive periodontitis (AgP) nuclear families and to investigate the influence of teeth with root abnormity on residual alveolar bone and the heredity of root abnormity, the premolar cone-root and proportion of crown and root. Nineteen AgP probands (9 males and 10 females) at average age of 24.5 and 38 parents at average age 51.0 were included. A full set of periapical radiographs of all the subjects were taken. The residual alveolar bone of each tooth was measured by the ratio (shown as percentage) of the distance between apical and the alveolar bone crest to the whole root length. The abnormity of roots was detected on a full set of periapical radiographs. All the roots and crowns of teeth were measured. The relationship between the residual bone and the ratio was studied. The heredity grade of the premolar cone-root, proportion of crown and root, and root abnormity were computed. The average residual alveolar bone of probands was less than that of their parents.In 11 families, the father's residual alveolar bone was less than that of the mother's. The average residual alveolar bone of the teeth with root abnormity was less than that of normal teeth. The average residual alveolar bone of the teeth with abnormity of roots and the normal teeth were (67.5 ± 22.2)% and (73.1 ± 18.7)% respectively, with statistical significance (P < 0.001). The heredity grade of the premolar cone-root was 40.1%, the heredity grade of proportion of crown and root was 46.8%, the heredity grade of root abnormity was 30.3%. The residual alveolar bone of the teeth with root abnormity was less than that of normal teeth in nuclear families. The heritability of the root abnormity, the cone-root and proportion of crown and root in our sample was 0.3-0.5, which means that genetic factors accounted for about one third to half of the efficiency for AgP.

  20. VRF ("Visual RobFit") — nuclear spectral analysis with non-linear full-spectrum nuclide shape fitting

    NASA Astrophysics Data System (ADS)

    Lasche, George; Coldwell, Robert; Metzger, Robert

    2017-09-01

    A new application (known as "VRF", or "Visual RobFit") for analysis of high-resolution gamma-ray spectra has been developed using non-linear fitting techniques to fit full-spectrum nuclide shapes. In contrast to conventional methods based on the results of an initial peak-search, the VRF analysis method forms, at each of many automated iterations, a spectrum-wide shape for each nuclide and, also at each iteration, it adjusts the activities of each nuclide, as well as user-enabled parameters of energy calibration, attenuation by up to three intervening or self-absorbing materials, peak width as a function of energy, full-energy peak efficiency, and coincidence summing until no better fit to the data can be obtained. This approach, which employs a new and significantly advanced underlying fitting engine especially adapted to nuclear spectra, allows identification of minor peaks that are masked by larger, overlapping peaks that would not otherwise be possible. The application and method are briefly described and two examples are presented.

  1. A Confrontation for Coexistence.

    ERIC Educational Resources Information Center

    Miller, Jen

    2003-01-01

    A month-long summer camp in Maine combines recreation, sports, and arts activities with daily conflict resolution sessions to help adolescents from regions of conflict (primarily the Middle East) learn the art of coexistence and peace. From its center in East Jerusalem, Seeds of Peace provides regular activities to reinforce the lessons that…

  2. A Confrontation for Coexistence.

    ERIC Educational Resources Information Center

    Miller, Jen

    2003-01-01

    A month-long summer camp in Maine combines recreation, sports, and arts activities with daily conflict resolution sessions to help adolescents from regions of conflict (primarily the Middle East) learn the art of coexistence and peace. From its center in East Jerusalem, Seeds of Peace provides regular activities to reinforce the lessons that…

  3. Use of NIMBY strategies to shape public perception of nuclear risk

    SciTech Connect

    Stevens, A.D. )

    1992-01-01

    In 1989 Rancho Seco became the US first operational nuclear power plant to be closed by a public initiative. This study analyzes how, after nearly 20 years of little public concern, community dissatisfaction grew to such a level that it eventually led to Rancho Seco's closure. The communicative process leading to closure was guided by the catalytic efforts of a local citizen action group that capitalized on key events at the plant and on the national level to define the issue of Rancho Seco's existence as one of excessive economic and safety risk. The local utility's defensive posture focused on public ignorance, which contributed to, instead of halting, the public's revocation of the utility's authority to operate the plant. Such acts of community defiance are on the rise and frequently yield success for groups employing NIMBY (Not In My Back Yard) strategies. The closure of Rancho Seco allows a case study analysis and evaluation of the communicative process by which NIMBYism can become an important source of sovereignty for communities who perceive themselves to be at risk.

  4. Evolution of ground state nuclear shapes in tungsten nuclei in terms of interacting boson model

    NASA Astrophysics Data System (ADS)

    Khalaf, A. M.; El-Shal, A. O.; Taha, M. M.; El-Sayed, M. A.

    2016-03-01

    The tungsten nuclei 180-190W are investigated within the framework of the interacting boson model using an intrinsic coherent state formalism. The Hamiltonian operator contains only multipole operators of the subalgebra associated with the dynamical symmetries SU(3) and O(6). The study includes the behavior of potential energy surfaces (BES's) and critical points in the space of the model parameters to declare the geometric character of the tungsten isotopic chain. Some selected energy levels and reduced E2 transition probabilities B(E2) for each nucleus are calculated to adjust the model parameters by using a computer code PH INT and simulated computer fitting programme to fit the experimental data with the IBM calculation by minimizing the root mean square deviations. The 180-190W isotopes lies in shape transition SU(3)-O(6) region of the IBM such that the lighter isotopes comes very clare to the SU(3) limit, while the behavior ones tend to be near the γ-unstable O(6) limit.

  5. U(5)-SU(3) nuclear shape transition within the interacting boson model applied to dysprosium isotopes

    NASA Astrophysics Data System (ADS)

    Kotb, M.

    2016-07-01

    In the framework of the interacting boson model (IBM) with intrinsic coherent state, the shape Hamiltonian from spherical vibrator U(5) to axially symmetric prolate deformed rotator SU(3) are examined. The Hamiltonian used is composed of a single boson energy term and quadrupole term. The potential energy surfaces (PES' s) corresponding to the U(5)-SU(3) transition are calculated with variation of a scaling and control parameters. The model is applied to 150-162Dy chain of isotopes. In this chain a change from spherical to well deformed nuclei is observed when moving from the lighter to heavier isotopes. 156Dy is a good candidate for the critical point symmetry X(5). The parameters of the model are determined by using a computer simulated search program in order to minimize the deviation between our calculated and some selected experimental energy levels, B(E2) transition rates and the two neutron separation energies S2n. We have also studied the energy ratios and the B(E2) values for the yrast state of the critical nucleus. The nucleon pair transfer intensities between ground-ground and ground-beta states are examined within IBM and boson intrinsic coherent framework.

  6. Phase coexistence in nuclei

    NASA Astrophysics Data System (ADS)

    Gulminelli, F.

    2004-11-01

    In this work the general theory of first order phase transitions in finite systems is discussed, with a special emphasis to the conceptual problems linked to a thermodynamic description for small, short-lived systems de-exciting in the vacuum as nuclear samples coming from heavy ion collisions. After a short review of the general theory of phase transitions in the framework of information theory, we will present the different possible extensions to the field of finite systems. The concept of negative heat capacity, developed in the early seventies in the context of self-gravitating systems, will be reinterpreted in the general framework of convexity anomalies of thermostatistical potentials. The connection with the distribution of the order parameter will lead us to a definition of first order phase transitions in finite systems based on topology anomalies of the event distribution in the space of observations. A careful study of the thermodynamic limit will provide a bridge with the standard theory of phase transitions and show that in a wide class of physical situations the different statistical ensembles are irreducibly inequivalent. In the second part of the paper we will apply the theoretical ideas developed in the first part to the possible observation of a liquid-to-gas-like phase transition in heavy ion collisions. The applicability of equilibrium concepts in a dynamical collisional process without boundary conditions will first be critically discussed. The observation of abnormally large partial energy fluctuations in carefully selected samples of collisions detected with the MULTICS-Miniball and INDRA array will then be reported as a strong evidence of a first order phase transition with negative heat capacity in the nuclear equation of state. Coexistence de phase dans les noyaux Ce papier présente une revue de la théorie générale des transitions de phase du premier ordre dans les petits systèmes, avec une attention particulière aux probl

  7. Effects of heat input on the microstructure and toughness of the 8 MnMoNi 5 5 shape-welded nuclear steel

    NASA Astrophysics Data System (ADS)

    Million, Karl; Datta, Ratan; Zimmermann, Horst

    2005-04-01

    A weld metal well proven in the German nuclear industry served as the basis for the certification of a shape-welded steel to be used as base material for manufacture of nuclear primary components. The outstanding properties of this steel are attributed to the extremely fine-grained and stable primary microstructure. Subsequent reheating cycles caused by neighbouring weld beads do neither lead to coarsened brittle structures in the heat-affected zone nor to increase in hardness and decrease in toughness, as is the case with wrought steel materials. One of the largest new reactor vessel design amongst today's advanced reactor projects is considered to be particularly suitable for the use of shape-welded parts in place of forgings. In addition the need for design and development of new shape-welded steel grades for other new generation reactor projects is emphasized, in which the experience gained with this research could make a contribution.

  8. Plant nuclear shape is independently determined by the SUN-WIP-WIT2-myosin XI-i complex and CRWN1

    PubMed Central

    Zhou, Xiao; Groves, Norman Reid; Meier, Iris

    2015-01-01

    Nuclei undergo dynamic shape changes during plant development, but the mechanism is unclear. In Arabidopsis, Sad1/UNC-84 (SUN) proteins, WPP domain-interacting proteins (WIPs), WPP domain-interacting tail-anchored proteins (WITs), myosin XI-i, and CROWDED NUCLEI 1 (CRWN1) have been shown to be essential for nuclear elongation in various epidermal cell types. It has been proposed that WITs serve as adaptors linking myosin XI-i to the SUN-WIP complex at the nuclear envelope (NE). Recently, an interaction between Arabidopsis SUN1 and SUN2 proteins and CRWN1, a plant analog of lamins, has been reported. Therefore, the CRWN1-SUN-WIP-WIT-myosin XI-i interaction may form a linker of the nucleoskeleton to the cytoskeleton complex. In this study, we investigate this proposed mechanism in detail for nuclei of Arabidopsis root hairs and trichomes. We show that WIT2, but not WIT1, plays an essential role in nuclear shape determination by recruiting myosin XI-i to the SUN-WIP NE bridges. Compared with SUN2, SUN1 plays a predominant role in nuclear shape. The NE localization of SUN1, SUN2, WIP1, and a truncated WIT2 does not depend on CRWN1. While crwn1 mutant nuclei are smooth, the nuclei of sun or wit mutants are invaginated, similar to the reported myosin XI-i mutant phenotype. Together, this indicates that the roles of the respective WIT and SUN paralogs have diverged in trichomes and root hairs, and that the SUN-WIP-WIT2-myosin XI-i complex and CRWN1 independently determine elongated nuclear shape. This supports a model of nuclei being shaped both by cytoplasmic forces transferred to the NE and by nucleoplasmic filaments formed under the NE. PMID:25759303

  9. Plant nuclear shape is independently determined by the SUN-WIP-WIT2-myosin XI-i complex and CRWN1.

    PubMed

    Zhou, Xiao; Groves, Norman Reid; Meier, Iris

    2015-01-01

    Nuclei undergo dynamic shape changes during plant development, but the mechanism is unclear. In Arabidopsis, Sad1/UNC-84 (SUN) proteins, WPP domain-interacting proteins (WIPs), WPP domain-interacting tail-anchored proteins (WITs), myosin XI-i, and CROWDED NUCLEI 1 (CRWN1) have been shown to be essential for nuclear elongation in various epidermal cell types. It has been proposed that WITs serve as adaptors linking myosin XI-i to the SUN-WIP complex at the nuclear envelope (NE). Recently, an interaction between Arabidopsis SUN1 and SUN2 proteins and CRWN1, a plant analog of lamins, has been reported. Therefore, the CRWN1-SUN-WIP-WIT-myosin XI-i interaction may form a linker of the nucleoskeleton to the cytoskeleton complex. In this study, we investigate this proposed mechanism in detail for nuclei of Arabidopsis root hairs and trichomes. We show that WIT2, but not WIT1, plays an essential role in nuclear shape determination by recruiting myosin XI-i to the SUN-WIP NE bridges. Compared with SUN2, SUN1 plays a predominant role in nuclear shape. The NE localization of SUN1, SUN2, WIP1, and a truncated WIT2 does not depend on CRWN1. While crwn1 mutant nuclei are smooth, the nuclei of sun or wit mutants are invaginated, similar to the reported myosin XI-i mutant phenotype. Together, this indicates that the roles of the respective WIT and SUN paralogs have diverged in trichomes and root hairs, and that the SUN-WIP-WIT2-myosin XI-i complex and CRWN1 independently determine elongated nuclear shape. This supports a model of nuclei being shaped both by cytoplasmic forces transferred to the NE and by nucleoplasmic filaments formed under the NE.

  10. Space mediates coexistence of females and hermaphrodites.

    PubMed

    Stewart-Cox, J A; Britton, N F; Mogie, M

    2005-11-01

    In gynodioecious populations of flowering plants females and hermaphrodites coexist. Gynodioecy is widespread and occurs in both asexual and sexual species but does not admit a satisfactory explanation from classical sex ratio theory. In sexual populations male fertility restoring genes have evolved to counter non-nuclear male sterility mutations. In pseudogamous asexual populations pollen retention and increased self-fertilization can make male sterility costly. Both of these mechanisms can promote coexistence. However, it remains unclear how either of these mechanisms could evolve if coexistence was not initially possible. In the absence of these adaptations non-spatial models predict that females either fail to invade hermaphrodite populations or else displace them until pollen shortage drives the population to extinction. We develop a pair approximation to a probabilistic cellular automata model in which females and hermaphrodites interact on a regular lattice. The model features independent pollination and colonization processes which take place on different timescales. The timescale separation is exploited to obtain, with perturbation methods, a more manageable aggregated pair approximation. We present both the mean field model which recreates the classical non-spatial predictions and the pair approximation, which strikingly predicts different invasion criteria and coexistence under a wide range of parameters. The pair approximation is shown to correspond well qualitatively with simulation behaviour.

  11. Electric monopole transitions: What they can tell us about nuclear structure

    SciTech Connect

    Zganjar, E.F.; Wood, J.L.

    1995-12-31

    A brief survey of E0 strength in a number of nuclei in different regions of the nuclear chart is presented. The connection between E0 strength and shape coexistence is reviewed. Nuclear structure information obtained from measurements of electric monopole transitions in {sup 184}Pt and {sup 187}Au is discussed. Plans for future experiments utilizing radioactive ion beams and E0 internal-pair-formation is presented.

  12. Pulse Shape Discrimination of Nuclear Recoil and Electron Recoil Events With a NaI(Tl) Crystal for Dark Matter Search

    NASA Astrophysics Data System (ADS)

    Kim, K. W.; Adhikari, G.; Adhikari, P.; Choi, S.; Ha, C.; Hahn, I. S.; Jeon, E. J.; Joo, H. W.; Kang, W. G.; Kim, H. J.; Kim, N. Y.; Kim, S. K.; Kim, Y. D.; Kim, Y. H.; Lee, H. S.; Lee, M. H.; Leonard, D. S.; Oh, S. Y.; Olsen, S. L.; Park, H. K.; Park, H. S.; Park, K. S.; Shim, J. H.; So, J. H.; Yoon, Y. S.

    2016-04-01

    In order to investigate discrimination between nuclear recoil and electron recoil events for the KIMS-NaI dark matter search experiment, we measured the pulse shapes produced by neutrons and gamma rays in a NaI(Tl) crystal. Relatively good pulse shape discrimination (PSD) power due to high light output of recently developed crystals makes it possible to test whether the annual modulation signal observed by the DAMA/LIBRA experiment is caused by nuclear recoil events. We applied the PSD to underground data taken with a 9.15 kg low-background and high-light-output NaI(Tl) crystal for 134 days. Good agreement between underground data and electron recoil events was observed.

  13. Measurement of the scintillation time spectra and pulse-shape discrimination of low-energy β and nuclear recoils in liquid argon with DEAP-1

    SciTech Connect

    Amaudruz, P. -A.; Batygov, M.; Beltran, B.; Bonatt, J.; Boudjemline, K.; Boulay, M. G.; Broerman, B.; Bueno, J. F.; Butcher, A.; Cai, B.; Caldwell, T.; Chen, M.; Chouinard, R.; Cleveland, B. T.; Cranshaw, D.; Dering, K.; Duncan, F.; Fatemighomi, N.; Ford, R.; Gagnon, R.; Giampa, P.; Giuliani, F.; Gold, M.; Golovko, V. V.; Gorel, P.; Grace, E.; Graham, K.; Grant, D. R.; Hakobyan, R.; Hallin, A. L.; Hamstra, M.; Harvey, P.; Hearns, C.; Hofgartner, J.; Jillings, C. J.; Kuźniak, M.; Lawson, I.; La Zia, F.; Li, O.; Lidgard, J. J.; Liimatainen, P.; Lippincott, W. H.; Mathew, R.; McDonald, A. B.; McElroy, T.; McFarlane, K.; McKinsey, D. N.; Mehdiyev, R.; Monroe, J.; Muir, A.; Nantais, C.; Nicolics, K.; Nikkel, J.; Noble, A. J.; O’Dwyer, E.; Olsen, K.; Ouellet, C.; Pasuthip, P.; Peeters, S. J. M.; Pollmann, T.; Rau, W.; Retière, F.; Ronquest, M.; Seeburn, N.; Skensved, P.; Smith, B.; Sonley, T.; Tang, J.; Vázquez-Jáuregui, E.; Veloce, L.; Walding, J.; Ward, M.

    2016-09-17

    The DEAP-1 low-background liquid argon detector has been used to measure scintillation pulse shapes of beta decays and nuclear recoil events and to demonstrate the feasibility of pulse-shape discrimination down to an electron-equivalent energy of 20 keVee. The relative intensities of singlet/triplet states in liquid argon have been measured as a function of energy between 15 and 500 keVee for both beta and nuclear recoils. Using a triple-coincidence tag we find the fraction of beta events that are misidentified as nuclear recoils to be less than 6 x 10-8 between 43-86 keVee and that the discrimination parameter agrees with a simple analytic model. The discrimination measurement is currently limited by nuclear recoils induced by cosmic-ray generated neutrons, and is expected to improve by operating the detector underground at SNOLAB. The analytic model predicts a beta misidentification fraction of 10-10 for an electron-equivalent energy threshold of 20 keVee. This reduction allows for a sensitive search for spin-independent scattering of WIMPs from 1000 kg of liquid argon with a WIMP-nucleon cross-section sensitivity of 10-46 cm2.

  14. Measurement of the scintillation time spectra and pulse-shape discrimination of low-energy β and nuclear recoils in liquid argon with DEAP-1

    DOE PAGES

    Amaudruz, P. -A.; Batygov, M.; Beltran, B.; ...

    2016-09-17

    The DEAP-1 low-background liquid argon detector has been used to measure scintillation pulse shapes of beta decays and nuclear recoil events and to demonstrate the feasibility of pulse-shape discrimination down to an electron-equivalent energy of 20 keVee. The relative intensities of singlet/triplet states in liquid argon have been measured as a function of energy between 15 and 500 keVee for both beta and nuclear recoils. Using a triple-coincidence tag we find the fraction of beta events that are misidentified as nuclear recoils to be less than 6 x 10-8 between 43-86 keVee and that the discrimination parameter agrees with amore » simple analytic model. The discrimination measurement is currently limited by nuclear recoils induced by cosmic-ray generated neutrons, and is expected to improve by operating the detector underground at SNOLAB. The analytic model predicts a beta misidentification fraction of 10-10 for an electron-equivalent energy threshold of 20 keVee. This reduction allows for a sensitive search for spin-independent scattering of WIMPs from 1000 kg of liquid argon with a WIMP-nucleon cross-section sensitivity of 10-46 cm2.« less

  15. The potential role of sexual conflict and sexual selection in shaping the genomic distribution of Mito-nuclear genes.

    PubMed

    Dean, Rebecca; Zimmer, Fabian; Mank, Judith E

    2014-05-01

    Mitochondrial interactions with the nuclear genome represent one of life's most important co-evolved mutualisms. In many organisms, mitochondria are maternally inherited, and in these cases, co-transmission between the mitochondrial and nuclear genes differs across different parts of the nuclear genome, with genes on the X chromosome having two-third probability of co-transmission, compared with one-half for genes on autosomes. These asymmetrical inheritance patterns of mitochondria and different parts of the nuclear genome have the potential to put certain gene combinations in inter-genomic co-adaptation or conflict. Previous work in mammals found strong evidence that the X chromosome has a dearth of genes that interact with the mitochondria (mito-nuclear genes), suggesting that inter-genomic conflict might drive genes off the X onto the autosomes for their male-beneficial effects. Here, we developed this idea to test coadaptation and conflict between mito-nuclear gene combinations across phylogenetically independent sex chromosomes on a far broader scale. We found that, in addition to therian mammals, only Caenorhabditis elegans showed an under-representation of mito-nuclear genes on the sex chromosomes. The remaining species studied showed no overall bias in their distribution of mito-nuclear genes. We discuss possible factors other than inter-genomic conflict that might drive the genomic distribution of mito-nuclear genes.

  16. The Co-Existence Daisy.

    ERIC Educational Resources Information Center

    Mahajna, Salah; Harel, Yael

    1992-01-01

    Activities that promote Arab-Jew coexistence at the English Department and Arab College at Beth Berl College are recounted. The authors' projects, each regarded as a petal in a "Coexistence Daisy," include those related to art encounters, interprofessional relationships, and inservice training. (LB)

  17. Measurement of the scintillation time spectra and pulse-shape discrimination of low-energy β and nuclear recoils in liquid argon with DEAP-1

    NASA Astrophysics Data System (ADS)

    Amaudruz, P.-A.; Batygov, M.; Beltran, B.; Bonatt, J.; Boudjemline, K.; Boulay, M. G.; Broerman, B.; Bueno, J. F.; Butcher, A.; Cai, B.; Caldwell, T.; Chen, M.; Chouinard, R.; Cleveland, B. T.; Cranshaw, D.; Dering, K.; Duncan, F.; Fatemighomi, N.; Ford, R.; Gagnon, R.; Giampa, P.; Giuliani, F.; Gold, M.; Golovko, V. V.; Gorel, P.; Grace, E.; Graham, K.; Grant, D. R.; Hakobyan, R.; Hallin, A. L.; Hamstra, M.; Harvey, P.; Hearns, C.; Hofgartner, J.; Jillings, C. J.; Kuźniak, M.; Lawson, I.; La Zia, F.; Li, O.; Lidgard, J. J.; Liimatainen, P.; Lippincott, W. H.; Mathew, R.; McDonald, A. B.; McElroy, T.; McFarlane, K.; McKinsey, D. N.; Mehdiyev, R.; Monroe, J.; Muir, A.; Nantais, C.; Nicolics, K.; Nikkel, J.; Noble, A. J.; O'Dwyer, E.; Olsen, K.; Ouellet, C.; Pasuthip, P.; Peeters, S. J. M.; Pollmann, T.; Rau, W.; Retière, F.; Ronquest, M.; Seeburn, N.; Skensved, P.; Smith, B.; Sonley, T.; Tang, J.; Vázquez-Jáuregui, E.; Veloce, L.; Walding, J.; Ward, M.

    2016-12-01

    The DEAP-1 low-background liquid argon detector was used to measure scintillation pulse shapes of electron and nuclear recoil events and to demonstrate the feasibility of pulse-shape discrimination down to an electron-equivalent energy of 20 keVee. In the surface dataset using a triple-coincidence tag we found the fraction of β events that are misidentified as nuclear recoils to be < 1.4 ×10-7 (90% C.L.) for energies between 43-86 keVee and for a nuclear recoil acceptance of at least 90%, with 4% systematic uncertainty on the absolute energy scale. The discrimination measurement on surface was limited by nuclear recoils induced by cosmic-ray generated neutrons. This was improved by moving the detector to the SNOLAB underground laboratory, where the reduced background rate allowed the same measurement to be done with only a double-coincidence tag. The combined data set contains 1.23 × 108 events. One of those, in the underground data set, is in the nuclear-recoil region of interest. Taking into account the expected background of 0.48 events coming from random pileup, the resulting upper limit on the level of electronic recoil contamination is < 2.7 ×10-8 (90% C.L.) between 44-89 keVee and for a nuclear recoil acceptance of at least 90%, with 6% systematic uncertainty on the absolute energy scale. We developed a general mathematical framework to describe pulse-shape-discrimination parameter distributions and used it to build an analytical model of the distributions observed in DEAP-1. Using this model, we project a misidentification fraction of approximately 10-10 for an electron-equivalent energy threshold of 15 keVee for a detector with 8 PE/keVee light yield. This reduction enables a search for spin-independent scattering of WIMPs from 1000 kg of liquid argon with a WIMP-nucleon cross-section sensitivity of 10-46 cm2, assuming negligible contribution from nuclear recoil backgrounds.

  18. Nuclear Aerosols: Direct Simulation and Elucidation of the Role of Multiple Components, Radioactivity, Charge, Shape and Spatial Inhomogeneity

    SciTech Connect

    Sudarshan K. Loyalka

    2008-10-12

    Nuclear aerosols can originate from severe core damae in light water reactors, core disruptive accidents in fast reactors, nuclear accidents during nuclear material transport, at waste disposal sites, or explosions. These aerosols evolve under natural transport processes as well as under the influence of engineered safety features. Such aerosols can be hazardous for the equipment inside the reactor, and when leaked into the environment, pose potential risks to the public. Hence, the origin, movement and distribution of these aerosols need to be studied and controlled.

  19. Nuclear structure research. Annual progress report

    SciTech Connect

    Wood, J.L.

    1996-12-31

    The most significant development this year has been the realization that EO transition strength is a fundamental manifestation of nuclear mean-square charge radius differences. Thus, EO transitions provide a fundamental signature for shape coexistence in nuclei. In this sense, EO transitions are second only to E2 transitions for signaling (quadrupole) shapes in nuclei and do so when shape differences occur. A major effort has been devoted to the review of EO transitions in nuclei. Experiments have been carried out or are scheduled at: ATLAS/FMA ({alpha} decay of very neutron-deficient Bi isotopes); MSU/NSCL ({beta} decay of {sup 56}Cu); and HRIBF/RMS (commissioning of tape collector, internal conversion/internal-pair spectrometer; {beta} decay of {sup 58}Cu). A considerable effort has been devoted to planning the nuclear structure physics that will be pursued using HRIBF. Theoretical investigations have continued in collaboration with Prof. K. Heyde, Prof. D.J. Rowe, Prof. J.O. Rasmussen, and Prof. P.B. Semmes. These studies focus on shape coexistence and particle-core coupling.

  20. Adaptive energy selective active contour with shape priors for nuclear segmentation and gleason grading of prostate cancer.

    PubMed

    Ali, Sahirzeeshan; Veltri, Robert; Epstein, Jonathan I; Christudass, Christhunesa; Madabhushi, Anant

    2011-01-01

    Shape based active contours have emerged as a natural solution to overlap resolution. However, most of these shape-based methods are computationally expensive. There are instances in an image where no overlapping objects are present and applying these schemes results in significant computational overhead without any accompanying, additional benefit. In this paper we present a novel adaptive active contour scheme (AdACM) that combines boundary and region based energy terms with a shape prior in a multi level set formulation. To reduce the computational overhead, the shape prior term in the variational formulation is only invoked for those instances in the image where overlaps between objects are identified; these overlaps being identified via a contour concavity detection scheme. By not having to invoke all 3 terms (shape, boundary, region) for segmenting every object in the scene, the computational expense of the integrated active contour model is dramatically reduced, a particularly relevant consideration when multiple objects have to be segmented on very large histopathological images. The AdACM was employed for the task of segmenting nuclei on 80 prostate cancer tissue microarray images. Morphological features extracted from these segmentations were found to able to discriminate different Gleason grade patterns with a classification accuracy of 84% via a Support Vector Machine classifier. On average the AdACM model provided 100% savings in computational times compared to a non-optimized hybrid AC model involving a shape prior.

  1. Scrotal insulation and its relationship to abnormal morphology, chromatin protamination and nuclear shape of spermatozoa in Holstein-Friesian and Belgian Blue bulls.

    PubMed

    Rahman, Mohammad Bozlur; Vandaele, Leen; Rijsselaere, Tom; Maes, Dominiek; Hoogewijs, Maarten; Frijters, Adrie; Noordman, Jakomien; Granados, Ana; Dernelle, Eric; Shamsuddin, Mohammed; Parrish, John J; Van Soom, Ann

    2011-10-15

    The objectives of this study were to identify the stages of spermatogenesis susceptible to elevated testicular temperature in terms of sperm motility, viability, morphology, chromatin protamination and nuclear shape. The latter two valuable parameters are not included in routine semen analysis. Scrotal insulation (SI) was applied for 48 h in 2 Holstein-Friesian (HF) and 2 Belgian Blue (BB) bulls and semen was collected at 7 d intervals along with semen collection of a non-insulated bull of each breed. Semen samples were frozen and assigned to 4 groups: period 1 (preinsulation) = -7 d and 0 d, where 0 d = initiation of SI after semen collection; period 2 = 7 d (sperm presumed in the epididymis during SI); period 3 = 14 d to 42 d (cells presumed at spermiogenesis and meiosis stages during SI); period 4 = 49 d to 63 d (cells presumed at spermatocytogenesis stage during SI). The percentages of progressively motile and viable spermatozoa as assessed by computer-assisted sperm analysis (CASA) and fluorescence microscopy, respectively were decreased whereas abnormal sperm heads, nuclear vacuoles and tail defects were increased at period 3 (P < 0.05) compared to period 1, 2 or 4 in SI bulls of both HF and BB breeds. Protamine deficient spermatozoa as observed by chromomycin A(3) (CMA(3)) staining were more present (P < 0.05) at period 2 and 3 in both breeds compared to period 1 or 4. Sperm nuclear shape as determined by Fourier harmonic amplitude (FHA) was most affected by heat stress during period 3 (P < 0.01) and a higher response was observed in BB bulls than HF bulls. In conclusion, sperm cells at the spermiogenic and meiotic stages of development are more susceptible to heat stress. The lack of chromatin protamination is the most pertinent result of heat stress, together with subtle changes in sperm head shape, which can be detected by FHA but not by conventional semen analysis.

  2. Coexistence under positive frequency dependence.

    PubMed Central

    Molofsky, J.; Bever, J. D.; Antonovics, J.

    2001-01-01

    Negative frequency dependence resulting from interspecific interactions is considered a driving force in allowing the coexistence of competitors. While interactions between species and genotypes can also result in positive frequency dependence, positive frequency dependence has usually been credited with hastening the extinction of rare types and is not thought to contribute to coexistence. In the present paper, we develop a stochastic cellular automata model that allows us to vary the scale of frequency dependence and the scale of dispersal. The results of this model indicate that positive frequency dependence will allow the coexistence of two species at a greater rate than would be expected from chance. This coexistence arises from the generation of banding patterns that will be stable over long time-periods. As a result, we found that positive frequency-dependent interactions over local spatial scales promote coexistence over neutral interactions. This result was robust to variation in boundary conditions within the simulation and to variation in levels of disturbance. Under all conditions, coexistence is enhanced as the strength of positive frequency-dependent interactions is increased. PMID:11217898

  3. Dynamic phase coexistence in glass-forming liquids.

    PubMed

    Pastore, Raffaele; Coniglio, Antonio; Ciamarra, Massimo Pica

    2015-07-09

    One of the most controversial hypotheses for explaining the heterogeneous dynamics of glasses postulates the temporary coexistence of two phases characterized by a high and by a low diffusivity. In this scenario, two phases with different diffusivities coexist for a time of the order of the relaxation time and mix afterwards. Unfortunately, it is difficult to measure the single-particle diffusivities to test this hypothesis. Indeed, although the non-Gaussian shape of the van-Hove distribution suggests the transient existence of a diffusivity distribution, it is not possible to infer from this quantity whether two or more dynamical phases coexist. Here we provide the first direct observation of the dynamical coexistence of two phases with different diffusivities, by showing that in the deeply supercooled regime the distribution of the single-particle diffusivities acquires a transient bimodal shape. We relate this distribution to the heterogeneity of the dynamics and to the breakdown of the Stokes-Einstein relation, and we show that the coexistence of two dynamical phases occurs up to a timescale growing faster than the relaxation time on cooling, for some of the considered models. Our work offers a basis for rationalizing the dynamics of supercooled liquids and for relating their structural and dynamical properties.

  4. Wetting Layers Close to Coexistence

    NASA Astrophysics Data System (ADS)

    Ripple, Dean Charles

    A substrate immersed in a two component liquid mixture will preferentially adsorb one of the components. I describe in this thesis theoretical and experimental results on the smooth divergence of the thickness of this adsorbed layer as the system is brought close to two phase coexistence. I present a free energy functional which combines a phenomenological equation of state suitable for near critical binary liquids with a mean field treatment of bulk and surface ions. For the system carbon disulfide plus nitromethane on glass, the theory agrees well with experiment for suitable choices of theoretical parameters. Electrical conductivity measurements of the coexisting liquid phases confirm the choice of ion concentration values. By driving a stirred binary liquid mixture off coexistence with a linear temperature ramp, very small perturbations off coexistence are possible. I apply this method to the system perfluoromethylcyclohexane plus methylcyclohexane on Si wafers, measuring the adsorption with DC null ellipsometry. As the distance from coexistence decreases, the layer thickness smoothly increases and shows a crossover from adsorption dominated by the nonzero correlation length to adsorption dominated by dispersion forces, in agreement with theoretical predictions.

  5. Interplay of order and chaos across a first-order quantum shape-phase transition in nuclei

    SciTech Connect

    Leviatan, A.; Macek, M.

    2012-10-20

    We study the nature of the dynamics in a first-order quantum phase transition between spherical and prolate-deformed nuclear shapes. Classical and quantum analyses reveal a change in the system from a chaotic Henon-Heiles behavior on the spherical side into a pronounced regular dynamics on the deformed side. Both order and chaos persist in the coexistence region and their interplay reflects the Landau potential landscape and the impact of collective rotations.

  6. Feasibility and coexistence of large ecological communities

    PubMed Central

    Grilli, Jacopo; Adorisio, Matteo; Suweis, Samir; Barabás, György; Banavar, Jayanth R.; Allesina, Stefano; Maritan, Amos

    2017-01-01

    The role of species interactions in controlling the interplay between the stability of ecosystems and their biodiversity is still not well understood. The ability of ecological communities to recover after small perturbations of the species abundances (local asymptotic stability) has been well studied, whereas the likelihood of a community to persist when the conditions change (structural stability) has received much less attention. Our goal is to understand the effects of diversity, interaction strengths and ecological network structure on the volume of parameter space leading to feasible equilibria. We develop a geometrical framework to study the range of conditions necessary for feasible coexistence. We show that feasibility is determined by few quantities describing the interactions, yielding a nontrivial complexity–feasibility relationship. Analysing more than 100 empirical networks, we show that the range of coexistence conditions in mutualistic systems can be analytically predicted. Finally, we characterize the geometric shape of the feasibility domain, thereby identifying the direction of perturbations that are more likely to cause extinctions. PMID:28233768

  7. Feasibility and coexistence of large ecological communities.

    PubMed

    Grilli, Jacopo; Adorisio, Matteo; Suweis, Samir; Barabás, György; Banavar, Jayanth R; Allesina, Stefano; Maritan, Amos

    2017-02-24

    The role of species interactions in controlling the interplay between the stability of ecosystems and their biodiversity is still not well understood. The ability of ecological communities to recover after small perturbations of the species abundances (local asymptotic stability) has been well studied, whereas the likelihood of a community to persist when the conditions change (structural stability) has received much less attention. Our goal is to understand the effects of diversity, interaction strengths and ecological network structure on the volume of parameter space leading to feasible equilibria. We develop a geometrical framework to study the range of conditions necessary for feasible coexistence. We show that feasibility is determined by few quantities describing the interactions, yielding a nontrivial complexity-feasibility relationship. Analysing more than 100 empirical networks, we show that the range of coexistence conditions in mutualistic systems can be analytically predicted. Finally, we characterize the geometric shape of the feasibility domain, thereby identifying the direction of perturbations that are more likely to cause extinctions.

  8. Learning to coexist with wildfire

    Treesearch

    M.A. Moritz; E. Batlloria; R.A. Bradstock; Jeff Stringer; Robbie Sitzlar; P.F. Hessburg; J. Leonard; S. McCaffrey; D.C. Odion; T. Schoennagel; A.D. Syphard

    2014-01-01

    The impacts of escalating wildfire in many regions — the lives and homes lost, the expense of suppression and the damage to ecosystem services — necessitate a more sustainable coexistence with wildfire. Climate change and continued development on fire-prone landscapes will only compound current problems. Emerging strategies for managing ecosystems and mitigating risks...

  9. Quantitative analysis of nuclear shape in oral squamous cell carcinoma is useful for predicting the chemotherapeutic response.

    PubMed

    Ogura, Maki; Yamamoto, Yoichiro; Miyashita, Hitoshi; Kumamoto, Hiroyuki; Fukumoto, Manabu

    2016-06-01

    The number of people afflicted with oral carcinoma in Japan has increased in recent years. Although preoperative neoadjuvant therapy with cisplatin and 5-fluorouracil are performed, chemotherapeutic response varies widely among the patients. With the aim of establishing novel indices to predict the therapeutic response to chemotherapy, we investigated the relationship between morphological features of pre-treatment oral carcinoma nuclei and the chemotherapeutic response using quantifying morphology of cell nuclei in pathological specimen images. We measured 4 morphological features of the nucleus of oral squamous cell carcinoma cases classified by the response to chemotherapy: No Change (NC) group, Partial Response (PR) group and Complete Response (CR) group. Furthermore, we performed immunohistochemical staining for p53 and Ki67 and calculated their positive rates in cancer tissues. Compactness and symmetry of the nucleus were significantly higher and nuclear edge response was significantly lower in cancer cells with lower chemotherapeutic responses compared high chemotherapeutic responders. As for positive rates of p53 and Ki67, there were no significant differences between any of the response groups. Morphological features of cancer cell nuclei in pathological specimens are sensitive predictive factors for the chemotherapeutic response to oral squamous cell carcinoma.

  10. Collagen Substrate Stiffness Anisotropy Affects Cellular Elongation, Nuclear Shape, and Stem Cell Fate toward Anisotropic Tissue Lineage.

    PubMed

    Islam, Anowarul; Younesi, Mousa; Mbimba, Thomas; Akkus, Ozan

    2016-09-01

    Rigidity of substrates plays an important role in stem cell fate. Studies are commonly carried out on isotropically stiff substrate or substrates with unidirectional stiffness gradients. However, many native tissues are anisotropically stiff and it is unknown whether controlled presentation of stiff and compliant material axes on the same substrate governs cytoskeletal and nuclear morphology, as well as stem cell differentiation. In this study, electrocompacted collagen sheets are stretched to varying degrees to tune the stiffness anisotropy (SA) in the range of 1 to 8, resulting in stiff and compliant material axes orthogonal to each other. The cytoskeletal aspect ratio increased with increasing SA by about fourfold. Such elongation was absent on cellulose acetate replicas of aligned collagen surfaces indicating that the elongation was not driven by surface topography. Mesenchymal stem cells (MSCs) seeded on varying anisotropy sheets displayed a dose-dependent upregulation of tendon-related markers such as Mohawk and Scleraxis. After 21 d of culture, highly anisotropic sheets induced greater levels of production of type-I, type-III collagen, and thrombospondin-4. Therefore, SA has direct effects on MSC differentiation. These findings may also have ramifications of stem cell fate on other anisotropically stiff tissues, such as skeletal/cardiac muscles, ligaments, and bone.

  11. Alpha-particle and proton probes of nuclear shapes in the rare earth and mass 80 regions

    SciTech Connect

    Sarantites, D.G.; Nicolis, N.G.; Abenante, V.; Majka, Z.; Semkow, T.M.; Baktash, C.; Beene, J.R.; Garcia-Bermudez, G.; Halbert, M.L.; Hensley, D.C.; Johnson, N.R.; Lee, I.Y.; McGowan, F.K.; Riley, M.A.; Virtanen, A.; Griffin, H.C.; Oak Ridge National Lab., TN; Michigan Univ., Ann Arbor, MI )

    1989-01-01

    Low emission barriers and large subbarrier anisotropies in the alpha-particle decay with respect to the spin direction, of Sn and rare earth compound nuclei, are examined in the light of recent calculations incorporating deformation. To explore the possibility of a correlation between the proton emission barriers and nuclear deformation, we studied proton spectra from the {sup 52}Cr({sup 34}S,2p2n){sup 82}Sr reaction. The proton spectra were observed with the Dwarf-Ball 4{pi} CsI(Tl) array, in coincidence with 18 Compton suppressed Ge detectors operated in conjunction with the Spin Spectrometer, a 4{pi} NaI(Tl) array. We found significant changes and shifts in the proton energy spectra as we selected gating transitions from bands of different moments of inertia or transitions from states of different spin in the same band. Substantial differences were also seen as a function of the {gamma}-ray multiplicity. These results are discussed in terms of statistical model calculations incorporating deformation and structure effects of the emitting system. 20 refs., 9 figs.

  12. In vitro developmental competence of pig nuclear transferred embryos: effects of GFP transfection, refrigeration, cell cycle synchronization and shapes of donor cells.

    PubMed

    Zhang, Yun-Hai; Pan, Deng-Ke; Sun, Xiu-Zhu; Sun, Guo-Jie; Liu, Xiao-Hui; Wang, Xiao-Bo; Tian, Xing-Hua; Li, Yan; Dai, Yun-Ping; Li, Ning

    2006-08-01

    The present study was designed to evaluate the feasibility of producing pig transgenic blastocysts expressing enhanced green fluorescent protein (GFP) and to examine the effects of shape and preparation methods of donor cells on in vitro developmental ability of pig nuclear transferred embryos (NTEs). In experiment 1, the effect of GFP transfection on development of pig NTEs was evaluated. The cleavage and blastocyst rates showed no significant difference between NTEs derived from transfected and non-transfected donors. In experiment 2, the effect of different nuclear donor preparation methods on in vitro development of NTEs was examined. The cleavage rate showed no statistically significant differences among three preparation methods. The blastocyst rates of donor cells treated once at -4 degrees C and those of freshly digested cells were similar to each other (26.3% vs 17.9%). The lowest blastocyst rates (5.88%) were observed when cells cryopreserved at -196 degrees C were used as donors. In experiment 3, the effect of different cell cycle synchronization methods on the in vitro development potential of pig NTEs was evaluated. The cleavage rate of NTEs derived from cycling cells was much better than that of NTEs derived from serum-starved cells (64.4% vs 50.5%, p < 0.05), but no significant difference was observed between the the blastocyst rates of the two groups. In experiment 4, the effect of different shapes of cultured fibroblast cells on the in vitro development of pig NTEs was examined. The fusion rate for couplets derived from rough cells was poorer than that observed in couplets derived from round smooth cells (47.8% vs 76.8%, p < 0.05). However, there were no significant differences observed in the cleavage rate and blastocyst rate. In conclusion, the present study indicated that (i) refrigerated pig GFP-transfected cells could be used as donors in nuclear transfer and these NTEs could be effectively developed to blastocyst stage; (ii) serum starvation

  13. Concealed configuration mixing and shape coexistence in the platinum nuclei

    SciTech Connect

    Garcia-Ramos, J. E.; Hellemans, V.; Heyde, K.

    2012-10-20

    The role of configuration mixing in the Pt region is investigated. The nature of the ground state changes smoothly, being spherical around mass A{approx} 174 and A{approx} 192 and deformed around the mid-shell N= 104 region. Interacting Boson Model with configuration mixing calculations are presented for deformations and isotope shifts. The assumption of the existence of two configurations with very different deformation provides a simple framework to explain the observed isotope shifts systematics.

  14. Probe of Triple Shape Coexistence In Neutron Deficient Polonium Nuclei

    SciTech Connect

    Wiseman, D. R.; Page, R. D.; Darby, I. G.; Andreyev, A. N.; Eeckhaudt, S.; Grahn, T.; Greenlees, P. T.; Jones, P.; Julin, R.; Juutinen, S.; Kettunen, H.; Leino, M.; Leppaenen, A.-P.; Nyman, M.; Pakarinen, J.; Rahkila, P.; Saren, J.; Scholey, C.; Uusitalo, J.; Sandzelius, M.

    2006-04-26

    {gamma}-ray transitions in the neutron deficient 190,197Po nuclei have been identified. The yrast band of 190Po has been extended up to a spin and parity of 14+ and is found to display similar systematic behaviour to isotones 186Hg and 188Pb above the 4+ level, thus confirming its prolate nature. In 197Po the band built upon the 13/2+ isomer has been extended up to a spin and parity of 33/2+, while the non-yrast side-band has been observed for the first time. The behaviour of 197Po is found to be similar to that of the nearby even-mass isotopes, which is consistent with the model in which the i13/2 neutron is weakly coupled to the states in the even-even core.

  15. Nuclear Pasta

    NASA Astrophysics Data System (ADS)

    da Silva Schneider, Andre; Horowitz, Charles; Berry, Don; Briggs, Christian

    2014-03-01

    For decades it has been theorized that just below nuclear saturation density matter undergoes a series of phase transitions. These phases, which are expected to exist in core-collapse supernovae and neutron stars, involve a range of exotic nuclear shapes collectively known as nuclear pasta. Recently, Jose Pons and collaborators suggested that ``the maximum period of isolated X-ray pulsars may be the first observational evidence for an amorphous inner crust, ..., possibly owing to the existence of a nuclear pasta phase.'' In this talk we present results of semi-classical molecular dynamics simulations of nuclear pasta and discuss how each phase might contribute to neutron star crust properties.

  16. Intraspecific density dependence and a guild of consumers coexisting on one resource.

    PubMed

    McPeek, Mark A

    2012-12-01

    The importance of negative intraspecific density dependence to promoting species coexistence in a community is well accepted. However, such mechanisms are typically omitted from more explicit models of community dynamics. Here I analyze a variation of the Rosenzweig-MacArthur consumer-resource model that includes negative intraspecific density dependence for consumers to explore its effect on the coexistence of multiple consumers feeding on a single resource. This analysis demonstrates that a guild of multiple consumers can easily coexist on a single resource if each limits its own abundance to some degree, and stronger intraspecific density dependence permits a wider variety of consumers to coexist. The mechanism permitting multiple consumers to coexist works in a fashion similar to apparent competition or to each consumer having its own specialized predator. These results argue for a more explicit emphasis on how negative intraspecific density dependence is generated and how these mechanisms combine with species interactions to shape overall community structure.

  17. The impact of consumer-resource cycles on the coexistence of competing consumers.

    PubMed

    Abrams, Peter A; Holt, Robert D

    2002-11-01

    This article seeks to determine the extent to which endogenous consumer-resource cycles can contribute to the coexistence of competing consumer species. It begins with a numerical analysis of a simple model proposed by Armstrong and McGehee. This model has a single resource and two consumers, one with a linear functional response and one with a saturating response. Coexistence of the two consumer species can occur when the species with a saturating response generates population cycles of the resource, and also has a lower resource requirement for zero population growth. Coexistence can be achieved over a wide range of relative efficiencies of the two consumers provided that the functional response of the saturating consumer reaches its half-saturation value when the resource population is a small fraction of its carrying capacity. In this case, the range of efficiencies allowing coexistence is comparable to that when two competitors have stable dynamics and a high degree of resource partitioning. A variety of modifications of this basic model are analyzed to investigate the consequences for coexistence of different resource growth equations, different functional and numerical response shapes, and other factors. Large differences in functional response shape appear to be the most important factor in producing robust coexistence via resource cycles. If the unstable species has a concave numerical response, this greatly expands the conditions allowing coexistence. If the stable consumer species has a convex (accelerating) functional and/or numerical response, the range of conditions allowing coexistence is also expanded. We argue that large between-species differences in functional response form can often be produced by between-consumer differences in the adaptive adjustments of foraging effort to food density. Consumer-resource cycles can also expand the conditions allowing coexistence when there is resource partitioning, but do so primarily when resource

  18. Cloning and Functional Analysis of Histones H3 and H4 in Nuclear Shaping during Spermatogenesis of the Chinese Mitten Crab, Eriocheir sinensis.

    PubMed

    Wu, Jiang-Li; Kang, Xian-Jiang; Guo, Ming-Shen; Mu, Shu-Mei; Zhang, Zhao-Hui

    2015-01-01

    During spermatogenesis in most animals, the basic proteins associated with DNA are continuously changing and somatic-typed histones are partly replaced by sperm-specific histones, which are then successively replaced by transition proteins and protamines. With the replacement of sperm nuclear basic proteins, nuclei progressively undergo chromatin condensation. The Chinese Mitten Crab (Eriocheir sinensis) is also known as the hairy crab or river crab (phylum Arthropoda, subphylum Crustacea, order Decapoda, and family Grapsidae). The spermatozoa of this species are aflagellate, and each has a spherical acrosome surrounded by a cup-shaped nucleus, peculiar to brachyurans. An interesting characteristic of the E. sinensis sperm nucleus is its lack of electron-dense chromatin. However, its formation is not clear. In this study, sequences encoding histones H3 and H4 were cloned by polymerase chain reaction amplification. Western blotting indicated that H3 and H4 existed in the sperm nuclei. Immunofluorescence and ultrastructural immunocytochemistry demonstrated that histones H3 and H4 were both present in the nuclei of spermatogonia, spermatocytes, spermatids and mature spermatozoa. The nuclear labeling density of histone H4 decreased in sperm nuclei, while histone H3 labeling was not changed significantly. Quantitative real-time PCR showed that the mRNA expression levels of histones H3 and H4 were higher at mitotic and meiotic stages than in later spermiogenesis. Our study demonstrates that the mature sperm nuclei of E. sinensis contain histones H3 and H4. This is the first report that the mature sperm nucleus of E. sinensis contains histones H3 and H4. This finding extends the study of sperm histones of E. sinensis and provides some basic data for exploring how decapod crustaceans form uncondensed sperm chromatin.

  19. Cloning and Functional Analysis of Histones H3 and H4 in Nuclear Shaping during Spermatogenesis of the Chinese Mitten Crab, Eriocheir sinensis

    PubMed Central

    Wu, Jiang-Li; Kang, Xian-Jiang; Guo, Ming-Shen; Mu, Shu-Mei; Zhang, Zhao-Hui

    2015-01-01

    During spermatogenesis in most animals, the basic proteins associated with DNA are continuously changing and somatic-typed histones are partly replaced by sperm-specific histones, which are then successively replaced by transition proteins and protamines. With the replacement of sperm nuclear basic proteins, nuclei progressively undergo chromatin condensation. The Chinese Mitten Crab (Eriocheir sinensis) is also known as the hairy crab or river crab (phylum Arthropoda, subphylum Crustacea, order Decapoda, and family Grapsidae). The spermatozoa of this species are aflagellate, and each has a spherical acrosome surrounded by a cup-shaped nucleus, peculiar to brachyurans. An interesting characteristic of the E. sinensis sperm nucleus is its lack of electron-dense chromatin. However, its formation is not clear. In this study, sequences encoding histones H3 and H4 were cloned by polymerase chain reaction amplification. Western blotting indicated that H3 and H4 existed in the sperm nuclei. Immunofluorescence and ultrastructural immunocytochemistry demonstrated that histones H3 and H4 were both present in the nuclei of spermatogonia, spermatocytes, spermatids and mature spermatozoa. The nuclear labeling density of histone H4 decreased in sperm nuclei, while histone H3 labeling was not changed significantly. Quantitative real-time PCR showed that the mRNA expression levels of histones H3 and H4 were higher at mitotic and meiotic stages than in later spermiogenesis. Our study demonstrates that the mature sperm nuclei of E. sinensis contain histones H3 and H4. This is the first report that the mature sperm nucleus of E. sinensis contains histones H3 and H4. This finding extends the study of sperm histones of E. sinensis and provides some basic data for exploring how decapod crustaceans form uncondensed sperm chromatin. PMID:25993499

  20. Learning to coexist with wildfire.

    PubMed

    Moritz, Max A; Batllori, Enric; Bradstock, Ross A; Gill, A Malcolm; Handmer, John; Hessburg, Paul F; Leonard, Justin; McCaffrey, Sarah; Odion, Dennis C; Schoennagel, Tania; Syphard, Alexandra D

    2014-11-06

    The impacts of escalating wildfire in many regions - the lives and homes lost, the expense of suppression and the damage to ecosystem services - necessitate a more sustainable coexistence with wildfire. Climate change and continued development on fire-prone landscapes will only compound current problems. Emerging strategies for managing ecosystems and mitigating risks to human communities provide some hope, although greater recognition of their inherent variation and links is crucial. Without a more integrated framework, fire will never operate as a natural ecosystem process, and the impact on society will continue to grow. A more coordinated approach to risk management and land-use planning in these coupled systems is needed.

  1. Intraspecific variation and species coexistence.

    PubMed

    Lichstein, Jeremy W; Dushoff, Jonathan; Levin, Simon A; Pacala, Stephen W

    2007-12-01

    We use a two-species model of plant competition to explore the effect of intraspecific variation on community dynamics. The competitive ability ("performance") of each individual is assigned by an independent random draw from a species-specific probability distribution. If the density of individuals competing for open space is high (e.g., because fecundity is high), species with high maximum (or large variance in) performance are favored, while if density is low, species with high typical (e.g., mean) performance are favored. If there is an interspecific mean-variance performance trade-off, stable coexistence can occur across a limited range of intermediate densities, but the stabilizing effect of this trade-off appears to be weak. In the absence of this trade-off, one species is superior. In this case, intraspecific variation can blur interspecific differences (i.e., shift the dynamics toward what would be expected in the neutral case), but the strength of this effect diminishes as competitor density increases. If density is sufficiently high, the inferior species is driven to extinction just as rapidly as in the case where there is no overlap in performance between species. Intraspecific variation can facilitate coexistence, but this may be relatively unimportant in maintaining diversity in most real communities.

  2. Competition drives clumpy species coexistence in estuarine phytoplankton.

    PubMed

    Segura, A M; Kruk, C; Calliari, D; García-Rodriguez, F; Conde, D; Widdicombe, C E; Fort, H

    2013-01-01

    Understanding the mechanisms that maintain biodiversity is a fundamental problem in ecology. Competition is thought to reduce diversity, but hundreds of microbial aquatic primary producers species coexist and compete for a few essential resources (e.g., nutrients and light). Here, we show that resource competition is a plausible mechanism for explaining clumpy distribution on individual species volume (a proxy for the niche) of estuarine phytoplankton communities ranging from North America to South America and Europe, supporting the Emergent Neutrality hypothesis. Furthermore, such a clumpy distribution was also observed throughout the Holocene in diatoms from a sediment core. A Lotka-Volterra competition model predicted position in the niche axis and functional affiliation of dominant species within and among clumps. Results support the coexistence of functionally equivalent species in ecosystems and indicate that resource competition may be a key process to shape the size structure of estuarine phytoplankton, which in turn drives ecosystem functioning.

  3. Microscopic description of nuclear shapes

    SciTech Connect

    Egido, J.L.; Robledo, L.M.; Valor, A.; Villafranca, A.

    1996-12-31

    The approximate particle number theory for density dependent forces is sketched, the theory is applied to discuss properties of the superdeformed ground state and excited bands of {sup 192}Hg. The force used in the calculations is the finite range density dependent Gogny force. The agreement with the available experimental results is very satisfactory.

  4. Deuteron NMR study of dynamics and of coexistence of paraelectric and ferroelectric phases in Rb0.90(ND4)0.10D2AsO4

    NASA Astrophysics Data System (ADS)

    Pinto, Nicholas J.; Howell, Francis L.; Schmidt, V. Hugo

    1993-09-01

    The deuteron glass Rb1-x(ND4)xD2AsO4 (DRADA) is a mixed crystal of RbD2AsO4 (DRDA) and ND4D2AsO4 (DADA). Deuteron nuclear magnetic resonance has been performed on the acid and ammonium deuterons. The crystal studied has an ammonium concentration (x=0.10) that puts it in the coexistence region of the phase diagram. Line-shape measurements of the ammonium deuterons show the coexistence of the ferroelectric (FE) and paraelectric (PE) phases as the temperature is lowered below the ferroelectric-phase-transition temperature Tc. The acid deuteron line shape on the other hand is found to broaden as the temperature is reduced but is unaffected by the ferroelectric transition. Spin-lattice-relaxation measurements have been performed and the activation energies for the relaxation processes have been computed. The relaxation-rate anomaly for acid deuterons in the ferroelectric-transition range indicates a short correlation length for the FE phase in the coexistence region of the phase diagram.

  5. Coexistent intracerebral metastatic melanoma and meningioma.

    PubMed

    Shinde, Sweety V; Shenoy, Asha S; Savant, Hemant V; Balasubramaniam, Srikant B

    2017-01-01

    Coexistence of multifocal neural crest tumors, namely meningioma, melanoma, and nerve sheath tumors, is termed as neurocristopathy. Neurofibromatosis is the commonest form of neurocristopathy. We report a rare case of frontal lobe metastatic melanoma coexistent with a parietal lobe meningioma, in the absence of any stigmata of neurofibromatosis.

  6. Nuclear structure research. Annual progress report

    SciTech Connect

    Wood, J.L.

    1995-07-31

    The most significant development this year has been the realization of a method for estimating EO transition strength in nuclei and the prediction that the de-excitation (draining) of superdeformed bands must take place, at least in some cases, by strong EO transitions. A considerable effort has been devoted to planning the nuclear structure physics that will be pursued using the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge. A significant effort has been devoted to HRIBF target development. This is a critical component of the HRIBF project. Exhaustive literature searches have been made for a variety of target materials with emphasis on thermodynamic properties. Vapor pressure measurements have been carried out. Experimental data sets for radioactive decays in the very neutron-deficient Pr-Eu and Ir-Tl regions have been under analysis. These decay schemes constitute parts of student Ph.D. theses. These studies are aimed at elucidating the onset of deformation in the Pr-Sm region and the characteristics of shape coexistence in the Ir-Bi region. Further experiments on shape coexistence in the neutron-deficient Ir-Bi region are planned using {alpha} decay studies at the FMA at ATLAS. The first experiment is scheduled for later this year.

  7. Spatial complementarity and the coexistence of species.

    PubMed

    Velázquez, Jorge; Garrahan, Juan P; Eichhorn, Markus P

    2014-01-01

    Coexistence of apparently similar species remains an enduring paradox in ecology. Spatial structure has been predicted to enable coexistence even when population-level models predict competitive exclusion if it causes each species to limit its own population more than that of its competitor. Nevertheless, existing hypotheses conflict with regard to whether clustering favours or precludes coexistence. The spatial segregation hypothesis predicts that in clustered populations the frequency of intra-specific interactions will be increased, causing each species to be self-limiting. Alternatively, individuals of the same species might compete over greater distances, known as heteromyopia, breaking down clusters and opening space for a second species to invade. In this study we create an individual-based model in homogeneous two-dimensional space for two putative sessile species differing only in their demographic rates and the range and strength of their competitive interactions. We fully characterise the parameter space within which coexistence occurs beyond population-level predictions, thereby revealing a region of coexistence generated by a previously-unrecognised process which we term the triadic mechanism. Here coexistence occurs due to the ability of a second generation of offspring of the rarer species to escape competition from their ancestors. We diagnose the conditions under which each of three spatial coexistence mechanisms operates and their characteristic spatial signatures. Deriving insights from a novel metric - ecological pressure - we demonstrate that coexistence is not solely determined by features of the numerically-dominant species. This results in a common framework for predicting, given any pair of species and knowledge of the relevant parameters, whether they will coexist, the mechanism by which they will do so, and the resultant spatial pattern of the community. Spatial coexistence arises from complementary combinations of traits in each species

  8. Spatial Complementarity and the Coexistence of Species

    PubMed Central

    Velázquez, Jorge; Garrahan, Juan P.; Eichhorn, Markus P.

    2014-01-01

    Coexistence of apparently similar species remains an enduring paradox in ecology. Spatial structure has been predicted to enable coexistence even when population-level models predict competitive exclusion if it causes each species to limit its own population more than that of its competitor. Nevertheless, existing hypotheses conflict with regard to whether clustering favours or precludes coexistence. The spatial segregation hypothesis predicts that in clustered populations the frequency of intra-specific interactions will be increased, causing each species to be self-limiting. Alternatively, individuals of the same species might compete over greater distances, known as heteromyopia, breaking down clusters and opening space for a second species to invade. In this study we create an individual-based model in homogeneous two-dimensional space for two putative sessile species differing only in their demographic rates and the range and strength of their competitive interactions. We fully characterise the parameter space within which coexistence occurs beyond population-level predictions, thereby revealing a region of coexistence generated by a previously-unrecognised process which we term the triadic mechanism. Here coexistence occurs due to the ability of a second generation of offspring of the rarer species to escape competition from their ancestors. We diagnose the conditions under which each of three spatial coexistence mechanisms operates and their characteristic spatial signatures. Deriving insights from a novel metric — ecological pressure — we demonstrate that coexistence is not solely determined by features of the numerically-dominant species. This results in a common framework for predicting, given any pair of species and knowledge of the relevant parameters, whether they will coexist, the mechanism by which they will do so, and the resultant spatial pattern of the community. Spatial coexistence arises from complementary combinations of traits in each

  9. Generic phase coexistence in the totally asymmetric kinetic Ising model

    NASA Astrophysics Data System (ADS)

    Godrèche, Claude; Luck, Jean-Marc

    2017-07-01

    The physical analysis of generic phase coexistence in the North-East-Center Toom model was originally given by Bennett and Grinstein. The gist of their argument relies on the dynamics of interfaces and droplets. We revisit the same question for a specific totally asymmetric kinetic Ising model on the square lattice. This nonequilibrium model possesses the remarkable property that its stationary-state measure in the absence of a magnetic field coincides with that of the usual ferromagnetic Ising model. We use both analytical arguments and numerical simulations in order to make progress in the quantitative understanding of the phenomenon of generic phase coexistence. At zero temperature a mapping onto the TASEP allows an exact determination of the time-dependent shape of the ballistic interface sweeping a large square minority droplet of up or down spins. At finite temperature, measuring the mean lifetime of such a droplet allows an accurate measurement of its shrinking velocity v, which depends on temperature T and magnetic field h. In the absence of a magnetic field, v vanishes with an exponent Δ_v≈2.5+/-0.2 as the critical temperature T c is approached. At fixed temperature in the ordered phase, v vanishes at the phase-boundary fields +/- h_b(T) which mark the limits of the coexistence region. The latter fields vanish with an exponent Δ_h≈3.2+/-0.3 as T c is approached.

  10. An evolutionary explanation of the aggregation model of species coexistence.

    PubMed Central

    Rohlfs, Marko; Hoffmeister, Thomas S

    2003-01-01

    In ecology, the 'aggregation model of coexistence' provides a powerful concept to explain the unexpectedly high species richness of insects on ephemeral resources like dung pats, fruits, etc. It suggests that females aggregate their eggs across resource patches, which leads to an increased intraspecific competition within occupied patches and a relatively large number of patches that remain unoccupied. This provides competitor-free patches for heterospecifics, facilitating species coexistence. At first glance, deliberately causing competition among the females' own offspring and leaving resources to heterospecific competitors seems altruistic and incompatible with individual fitness maximization, raising the question of how natural selection operates in favour of egg aggregation on ephemeral resource patches. Allee effects that lead to fitness maxima at intermediate egg densities have been suggested, but not yet detected. Using drosophilid flies on decaying fruits as a study system, we demonstrate a hump-shaped relationship between egg density and individual survival probability, with maximum survivorship at intermediate densities. This pattern clearly selects for egg aggregation and resolves the possible conflict between the ecological concept of species coexistence on ephemeral resources and evolutionary theory. PMID:12952629

  11. Intermittent control of coexisting attractors.

    PubMed

    Liu, Yang; Wiercigroch, Marian; Ing, James; Pavlovskaia, Ekaterina

    2013-06-28

    This paper proposes a new control method applicable for a class of non-autonomous dynamical systems that naturally exhibit coexisting attractors. The central idea is based on knowledge of a system's basins of attraction, with control actions being applied intermittently in the time domain when the actual trajectory satisfies a proximity constraint with regards to the desired trajectory. This intermittent control uses an impulsive force to perturb one of the system attractors in order to switch the system response onto another attractor. This is carried out by bringing the perturbed state into the desired basin of attraction. The method has been applied to control both smooth and non-smooth systems, with the Duffing and impact oscillators used as examples. The strength of the intermittent control force is also considered, and a constrained intermittent control law is introduced to investigate the effect of limited control force on the efficiency of the controller. It is shown that increasing the duration of the control action and/or the number of control actuations allows one to successfully switch between the stable attractors using a lower control force. Numerical and experimental results are presented to demonstrate the effectiveness of the proposed method.

  12. Competitive coexistence in stoichiometric chaos.

    PubMed

    Deng, Bo; Loladze, Irakli

    2007-09-01

    Classical predator-prey models, such as Lotka-Volterra, track the abundance of prey, but ignore its quality. Yet, in the past decade, some new and occasionally counterintuitive effects of prey quality on food web dynamics emerged from both experiments and mathematical modeling. The underpinning of this work is the theory of ecological stoichiometry that is centered on the fact that each organism is a mixture of multiple chemical elements such as carbon (C), nitrogen (N), and phosphorus (P). The ratios of these elements can vary within and among species, providing simple ways to represent prey quality as its C:N or C:P ratios. When these ratios modeled to vary, as they frequently do in nature, seemingly paradoxical results can arise such as the extinction of a predator that has an abundant and accessible prey. Here, for the first time, we show analytically that the reduction in prey quality can give rise to chaotic oscillations. In particular, when competing predators differ in their sensitivity to prey quality then all species can coexist via chaotic fluctuations. The chaos generating mechanism is based on the existence of a junction-fold point on the nullcline surfaces of the species. Conditions on parameters are found for such a point, and the singular perturbation method and the kneading sequence analysis are used to demonstrate the existence of a period-doubling cascade to chaos as a result of the point.

  13. A theoretical study of rotational diffusion models for rod-shaped viruses. The influence of motion on 31P nuclear magnetic resonance lineshapes and transversal relaxation.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1993-01-01

    Information about the interaction between nucleic acids and coat proteins in intact virus particles may be obtained by studying the restricted backbone dynamics of the incapsulated nucleic acids using 31P nuclear magnetic resonance (NMR) spectroscopy. In this article, simulations are carried out to investigate how reorientation of a rod-shaped virus particle as a whole and isolated nucleic acid motions within the virion influence the 31P NMR lineshape and transversal relaxation dominated by the phosphorus chemical shift anisotropy. Two opposite cases are considered on a theoretical level. First, isotropic rotational diffusion is used as a model for mobile nucleic acids that are loosely or partially bound to the protein coat. The effect of this type of diffusion on lineshape and transversal relaxation is calculated by solving the stochastic Liouville equation by an expansion in spherical functions. Next, uniaxial rotational diffusion is assumed to represent the mobility of phosphorus in a virion that rotates as a rigid rod about its length axis. This type of diffusion is approximated by an exchange process among discrete sites. As turns out from these simulations, the amplitude and the frequency of the motion can only be unequivocally determined from experimental data by a combined analysis of the lineshape and the transversal relaxation. In the fast motional region both the isotropic and the uniaxial diffusion model predict the same transversal relaxation as the Redfield theory. For very slow motion, transversal relaxation resembles the nonexponential relaxation as observed for water molecules undergoing translational diffusion in a magnetic field gradient. In this frequency region T2e is inversely proportional to the cube root of the diffusion coefficient. In addition to the isotropic and uniaxial diffusion models, a third model is presented, in which fast restricted nucleic acid backbone motions dominating the lineshape are superimposed on a slow rotation of the

  14. Physical layer simulation study for the coexistence of WLAN standards

    SciTech Connect

    Howlader, M. K.; Keiger, C.; Ewing, P. D.; Govan, T. V.

    2006-07-01

    This paper presents the results of a study on the performance of wireless local area network (WLAN) devices in the presence of interference from other wireless devices. To understand the coexistence of these wireless protocols, simplified physical-layer-system models were developed for the Bluetooth, Wireless Fidelity (WiFi), and Zigbee devices, all of which operate within the 2.4-GHz frequency band. The performances of these protocols were evaluated using Monte-Carlo simulations under various interference and channel conditions. The channel models considered were basic additive white Gaussian noise (AWGN), Rayleigh fading, and site-specific fading. The study also incorporated the basic modulation schemes, multiple access techniques, and channel allocations of the three protocols. This research is helping the U.S. Nuclear Regulatory Commission (NRC) understand the coexistence issues associated with deploying wireless devices and could prove useful in the development of a technical basis for guidance to address safety-related issues with the implementation of wireless systems in nuclear facilities. (authors)

  15. Nuclear Speckles

    PubMed Central

    Spector, David L.; Lamond, Angus I.

    2011-01-01

    Nuclear speckles, also known as interchromatin granule clusters, are nuclear domains enriched in pre-mRNA splicing factors, located in the interchromatin regions of the nucleoplasm of mammalian cells. When observed by immunofluorescence microscopy, they usually appear as 20–50 irregularly shaped structures that vary in size. Speckles are dynamic structures, and their constituents can exchange continuously with the nucleoplasm and other nuclear locations, including active transcription sites. Studies on the composition, structure, and dynamics of speckles have provided an important paradigm for understanding the functional organization of the nucleus and the dynamics of the gene expression machinery. PMID:20926517

  16. Phase Coexistence in the Mixed Crystal RUBIDIUM(1-X) Ammonium(x) Dihydrogen Arsenate

    NASA Astrophysics Data System (ADS)

    Pinto, Nicholas Joaquim

    1992-01-01

    A study of the coexistence phenomenon in mixed crystals of rubidium ammonium dihydrogen arsenate has been done. Coexistence in this study refers to the simultaneous presence of ferroelectric and proton glass phases as temperature is lowered below the ferroelectric phase transition temperature T_{c}. Such coexistence is found to exist in these mixed crystals only for small ammonium concentrations. Our results show that coexistence exists for lower ammonium concentration than previously suggested. A study was also done on crystals with larger ammonium concentrations that show pure proton glass behavior and the results compared with the coexistence phenomenon. Dielectric, spontaneous polarization and nuclear magnetic resonance experiments on mixed crystals with small ammonium concentrations show that at low temperatures there exists intimate coexistence of ferroelectric clusters with proton glass clusters below the glass transition temperature T_{g}. In the proton glass phase, we observe a spread of relaxation times due to the creation and annihilation of HAsO_4 and H_3AsO_4 pairs as they diffuse through the crystal. Spin lattice relaxation times for the acid deuterons in a 10% ammoniated sample show a broad T_1 minimum near the glass transition temperature which is characteristic of proton glasses. Field-cooling experiments were also done on the pure proton glass. The results are consistent with dielectric measurements, but the remanent polarization was found to be extremely small. This polarization was found to depend on the rate of heating and cooling the sample while performing the experiment.

  17. Equilibrium coexistence of three amphiboles

    USGS Publications Warehouse

    Robinson, P.; Jaffe, H.W.; Klein, C.; Ross, M.

    1969-01-01

    Electron probe and wet chemical analyses of amphibole pairs from the sillimanite zone of central Massachusetts and adjacent New Hampshire indicated that for a particular metamorphic grade there should be a restricted composition range in which three amphiboles can coexist stably. An unequivocal example of such an equilibrium three amphibole rock has been found in the sillimanite-orthoclase zone. It contains a colorless primitive clinoamphibole, space group P21/m, optically and chemically like cummingtonite with blue-green hornblende exsolution lamellae on (100) and (-101) of the host; blue-green hornblende, space group C2/m, with primitive cummingtonite exsolution lamellae on (100) and (-101) of the host; and pale pinkish tan anthophyllite, space group Pnma, that is free of visible exsolution lamellae but is a submicroscopic intergrowth of two orthorhombic amphiboles. Mutual contacts and coarse, oriented intergrowths of two and three host amphiboles indicate the three grew as an equilibrium assemblage prior to exsolution. Electron probe analyses at mutual three-amphibole contacts showed little variation in the composition of each amphibole. Analyses believed to represent most closely the primary amphibole compositions gave atomic proportions on the basis of 23 oxygens per formula unit as follows: for primitive cummingtonite (Na0.02Ca0.21- Mn0.06Fe2+2.28Mg4.12Al0.28) (Al0.17Si7.83), for hornblende (Na0.35Ca1.56Mn0.02Fe1.71Mg2.85Al0.92) (Al1.37Si6.63), and for anthophyllite (Na0.10Ca0.06Mn0.06Fe2.25Mg4.11Al0.47) (Al0.47Si7.53). The reflections violating C-symmetry, on X-ray single crystal photographs of the primitive cummingtonite, are weak and diffuse, and suggest a partial inversion from a C-centered to a primitive clinoamphibole. Single crystal photographs of the anthophyllite show split reflections indicating it is an intergrowth of about 80% anthophyllite and about 20% gedrite which differ in their b crystallographic dimensions. Split reflections are

  18. Energetic Constraints on Species Coexistence in Birds

    PubMed Central

    Pigot, Alexander L.

    2016-01-01

    The association between species richness and ecosystem energy availability is one of the major geographic trends in biodiversity. It is often explained in terms of energetic constraints, such that coexistence among competing species is limited in low productivity environments. However, it has proven challenging to reject alternative views, including the null hypothesis that species richness has simply had more time to accumulate in productive regions, and thus the role of energetic constraints in limiting coexistence remains largely unknown. We use the phylogenetic relationships and geographic ranges of sister species (pairs of lineages who are each other’s closest extant relatives) to examine the association between energy availability and coexistence across an entire vertebrate class (Aves). We show that the incidence of coexistence among sister species increases with overall species richness and is elevated in more productive ecosystems, even when accounting for differences in the evolutionary time available for coexistence to occur. Our results indicate that energy availability promotes species coexistence in closely related lineages, providing a key step toward a more mechanistic understanding of the productivity–richness relationship underlying global gradients in biodiversity. PMID:26974194

  19. Nuclear shape, growth and integrity in the closed mitosis of fission yeast depend on the Ran-GTPase system, the spindle pole body and the endoplasmic reticulum.

    PubMed

    Gonzalez, Yanira; Meerbrey, Kristen; Chong, Jennifer; Torii, Yoshihiro; Padte, Neal N; Sazer, Shelley

    2009-07-15

    The double lipid bilayer of the nuclear envelope (NE) remains intact during closed mitosis. In the fission yeast Schizosaccharomyces pombe, the intranuclear mitotic spindle has envelope-embedded spindle pole bodies (SPB) at its ends. As the spindle elongates and the nucleus divides symmetrically, nuclear volume remains constant but nuclear area rapidly increases by 26%. When Ran-GTPase function is compromised in S. pombe, nuclear division is strikingly asymmetrical and the newly synthesized SPB is preferentially associated with the smaller nucleus, indicative of a Ran-dependent SPB defect that interferes with symmetrical nuclear division. A second defect, which specifically influences the NE, results in breakage of the NE upon spindle elongation. This defect, but not asymmetric nuclear division, is partially rescued by slowing spindle elongation, stimulating endoplasmic reticulum (ER) proliferation or changing conformation of the ER membrane. We propose that redistribution of lipid within the ER-NE network is crucial for mitosis-specific NE changes in both open and closed mitosis.

  20. Linking metacommunity paradigms to spatial coexistence mechanisms.

    PubMed

    Shoemaker, Lauren G; Melbourne, Brett A

    2016-09-01

    Four metacommunity paradigms-usually called neutral, species sorting, mass effects, and patch dynamics, respectively-are widely used for empirical and theoretical studies of spatial community dynamics. The paradigm framework highlights key ecological mechanisms operating in metacommunities, such as dispersal limitation, competition-colonization tradeoffs, or species equivalencies. However, differences in coexistence mechanisms between the paradigms and in situations with combined influences of multiple paradigms are not well understood. Here, we create a common model for competitive metacommunities, with unique parameterizations for each metacommunity paradigm and for scenarios with multiple paradigms operating simultaneously. We derive analytical expressions for the strength of Chesson's spatial coexistence mechanisms and quantify these for each paradigm via simulation. For our model, fitness-density covariance, a concentration effect measuring the importance of intraspecific aggregation of individuals, is the dominant coexistence mechanism in all three niche-based metacommunity paradigms. Increased dispersal between patches erodes intraspecific aggregation, leading to lower coexistence strength in the mass effects paradigm compared to species sorting. Our analysis demonstrates the potential importance of aggregation of individuals (fitness-density covariance) over co-variation in abiotic environments and competition between species (the storage effect), as fitness-density covariance can be stronger than the storage effect and is the sole stabilizing mechanism in the patch dynamics paradigm. As expected, stable coexistence does not occur in the neutral paradigm, which requires species to be equal and emphasizes the role of stochasticity. We show that stochasticity also plays an important role in niche-structured metacommunities by altering coexistence strength. We conclude that Chesson's spatial coexistence mechanisms provide a flexible framework for comparing

  1. Coexistence of antiferromagnetic and ferromagnetic spin correlations in Ca(Fe1-xCox)2As2 revealed by As75 nuclear magnetic resonance

    SciTech Connect

    Cui, J.; Wiecki, P.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.; Furukawa, Y.

    2016-11-22

    Recent nuclear magnetic resonance (NMR) measurements revealed the coexistence of stripe-type antiferromagnetic (AFM) and ferromagnetic (FM) spin correlations in both the hole- and electron-doped BaFe 2 As 2 families of iron-pnictide superconductors by a Korringa ratio analysis. Motivated by the NMR work, we investigate the possible existence of FM fluctuations in another iron-pnictide superconducting family, Ca ( Fe 1 - x Co x ) 2 As 2 . We reanalyzed our previously reported data in terms of the Korringa ratio and found clear evidence for the coexistence of stripe-type AFM and FM spin correlations in the electron-doped CaFe 2 As 2 system. These NMR data indicate that FM fluctuations exist in general in iron-pnictide superconducting families and thus must be included to capture the phenomenology of the iron pnictides.

  2. Blocking protein farnesylation improves nuclear shape abnormalities in keratinocytes of mice expressing the prelamin A variant in Hutchinson-Gilford progeria syndrome.

    PubMed

    Wang, Yuexia; Ostlund, Cecilia; Worman, Howard J

    2010-01-01

    Hutchinson-Gilford progeria syndrome (HGPS) is an accelerated aging disorder caused by mutations in LMNA leading to expression of a truncated prelamin A variant termed progerin. Whereas a farnesylated polypeptide is normally removed from the carboxyl-terminus of prelamin A during endoproteolytic processing to lamin A, progerin lacks the cleavage site and remains farnesylated. Cultured cells from human subjects with HGPS and genetically modified mice expressing progerin have nuclear morphological abnormalities, which are reversed by inhibitors of protein farnesylation. In addition, treatment with protein farnesyltransferase inhibitors improves whole animal phenotypes in mouse models of HGPS. However, improvement in nuclear morphology in tissues after treatment of animals has not been demonstrated. We therefore treated transgenic mice that express progerin in epidermis with the protein farnesyltransferase inhibitor FTI-276 or a combination of pravastatin and zoledronate to determine if they reversed nuclear morphological abnormalities in tissue. Immunofluorescence microscopy and "blinded" electron microscopic analysis demonstrated that systemic administration of FTI-276 or pravastatin plus zoledronate significantly improved nuclear morphological abnormalities in keratinocytes of transgenic mice. These results show that pharmacological blockade of protein prenylation reverses nuclear morphological abnormalities that occur in HGPS in vivo. They further suggest that skin biopsy may be useful to determine if protein farnesylation inhibitors are exerting effects in subjects with HGPS in clinical trials.

  3. Shaping the nucleus: factors and forces.

    PubMed

    Walters, Alison D; Bommakanti, Ananth; Cohen-Fix, Orna

    2012-09-01

    Take a look at a textbook illustration of a cell and you will immediately be able to locate the nucleus, which is often drawn as a spherical or ovoid shaped structure. But not all cells have such nuclei. In fact, some disease states are diagnosed by the presence of nuclei that have an abnormal shape or size. What defines nuclear shape and nuclear size, and how does nuclear geometry affect nuclear function? While the answer to the latter question remains largely unknown, significant progress has been made towards understanding the former. In this review, we provide an overview of the factors and forces that affect nuclear shape and size, discuss the relationship between ER structure and nuclear morphology, and speculate on the possible connection between nuclear size and its shape. We also note the many interesting questions that remain to be explored. Copyright © 2012 Wiley Periodicals, Inc.

  4. Species coexistence in temperate, mixed deciduous forests.

    PubMed

    Nakashizuka, T

    2001-04-01

    The response of tree life-history traits to community profiles (horizontal and vertical heterogeneity, disturbances and biotic interactions) determines community assembly rules, which are currently a hot issue in community ecology. Important mechanisms of coexistence differ throughout the developing stages of tree life history. Many processes of niche partitioning and tradeoffs that potentially enable tree coexistence have been reported to be present in temperate forests, although some of these life-history traits are either correlated with each other or are not independent. Not all of the proposed mechanisms explain coexistence equally well; some could predominate in determining the community organization of forest communities. Population studies need to concentrate more on the component species of a target community to detect the ecological assembly rule. These approaches can also address how chance factors contribute to the composition of temperate tree communities, which might be less dependent on chance than are tropical ones.

  5. Behavioral refuges and predator-prey coexistence.

    PubMed

    Křivan, Vlastimil

    2013-12-21

    The effects of a behavioral refuge caused either by the predator optimal foraging or prey adaptive antipredator behavior on the Gause predator-prey model are studied. It is shown that both of these mechanisms promote predator-prey coexistence either at an equilibrium, or along a limit cycle. Adaptive prey refuge use leads to hysteresis in prey antipredator behavior which allows predator-prey coexistence along a limit cycle. Similarly, optimal predator foraging leads to sigmoidal functional responses with a potential to stabilize predator-prey population dynamics at an equilibrium, or along a limit cycle.

  6. Sizing and shaping the nucleus: mechanisms and significance.

    PubMed

    Jevtić, Predrag; Edens, Lisa J; Vuković, Lidija D; Levy, Daniel L

    2014-06-01

    The size and shape of the nucleus are tightly regulated, indicating the physiological significance of proper nuclear morphology, yet the mechanisms and functions of nuclear size and shape regulation remain poorly understood. Correlations between altered nuclear morphology and certain disease states have long been observed, most notably many cancers are diagnosed and staged based on graded increases in nuclear size. Here we review recent studies investigating the mechanisms regulating nuclear size and shape, how mitotic events influence nuclear morphology, and the role of nuclear size and shape in subnuclear chromatin organization and cancer progression. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. The effects of colonization, extinction and competition on co-existence in metacommunities.

    PubMed

    Hunt, Julia J F G; Bonsall, Michael B

    2009-07-01

    1. The co-existence of competitors in heterogeneous landscapes depends on the processes of colonization, extinction and spatial scale. In this study, we explore the metapopulation dynamics of competitive interactions. 2. Rather than simply evaluating the outcome of interspecific competition in the traditional manner, we focus on both the local population dynamic effects and the regional metapopulation processes affecting species co-existence. 3. We develop a theoretical model of regional co-existence to generate a set of predictions on the patterns of colonization necessary for co-existence and the regional processes that can lead to competitive exclusion. We empirically test these predictions using metacommunity microcosms of the interaction between two bruchid beetles (Callosobruchus chinensis, Callosobruchus maculatus). 4. Using well-replicated time series of the interaction between the bruchids and statistical methods of model fitting, we show how the qualitative and quantitative pattern of interspecific competition between the bruchid beetles is shaped by the structure of the metacommunity. 5. In unlimited dispersal metacommunities, the global exclusion of the inferior competitor is shown to be influenced more by the processes associated with extinction rather than low colonization ability. In restricted dispersal metacommunities, we show how the co-existence of competitors in a spatially heterogeneous habitat (patches connected through limited dispersal) is affected by Allee effects and life-history [colonization (dispersal) - competition] trade-offs.

  8. How variation between individuals affects species coexistence.

    PubMed

    Hart, Simon P; Schreiber, Sebastian J; Levine, Jonathan M

    2016-08-01

    Although the effects of variation between individuals within species are traditionally ignored in studies of species coexistence, the magnitude of intraspecific variation in nature is forcing ecologists to reconsider. Compelling intuitive arguments suggest that individual variation may provide a previously unrecognised route to diversity maintenance by blurring species-level competitive differences or substituting for species-level niche differences. These arguments, which are motivating a large body of empirical work, have rarely been evaluated with quantitative theory. Here we incorporate intraspecific variation into a common model of competition and identify three pathways by which this variation affects coexistence: (1) changes in competitive dynamics because of nonlinear averaging, (2) changes in species' mean interaction strengths because of variation in underlying traits (also via nonlinear averaging) and (3) effects on stochastic demography. As a consequence of the first two mechanisms, we find that intraspecific variation in competitive ability increases the dominance of superior competitors, and intraspecific niche variation reduces species-level niche differentiation, both of which make coexistence more difficult. In addition, individual variation can exacerbate the effects of demographic stochasticity, and this further destabilises coexistence. Our work provides a theoretical foundation for emerging empirical interests in the effects of intraspecific variation on species diversity.

  9. Dispersal-mediated coexistence of competing predators.

    PubMed

    Namba, Toshiyuki; Hashimoto, Chiemi

    2004-08-01

    Models of metapopulations have often ignored local community dynamics and spatial heterogeneity among patches. However, persistence of a community as a whole depends both on the local interactions and the rates of dispersal between patches. We study a mathematical model of a metacommunity with two consumers exploiting a resource in a habitat of two different patches. They are the exploitative competitors or the competing predators indirectly competing through depletion of the shared resource. We show that they can potentially coexist, even if one species is sufficiently inferior to be driven extinct in both patches in isolation, when these patches are connected through diffusive dispersal. Thus, dispersal can mediate coexistence of competitors, even if both patches are local sinks for one species because of the interactions with the other species. The spatial asynchrony and the competition-colonization trade-off are usual mechanisms to facilitate regional coexistence. However, in our case, two consumers can coexist either in synchronous oscillation between patches or in equilibrium. The higher dispersal rate of the superior prompts rather than suppresses the inferior. Since differences in the carrying capacity between two patches generate flows from the more productive patch to the less productive, loss of the superior by emigration relaxes competition in the former, and depletion of the resource by subsidized consumers decouples the local community in the latter.

  10. Ultrasonic features of papillary thyroid microcarcinoma coexisting with a thyroid abnormality

    PubMed Central

    Li, Bo; Zhang, Yaqiong; Yin, Ping; Zhou, Jian; Jiang, Tian'an

    2016-01-01

    The present study aimed to investigate the value of ultrasonography in the diagnosis of papillary thyroid microcarcinoma (PTMC) coexisting with a thyroid abnormality, and to improve the accuracy of PTMC diagnosis. The ultrasonic features of 38 PTMC nodules coexisting with a thyroid abnormality and 56 thyroid benign nodules, obtained by surgical resection and confirmed by pathological analysis, were retrospectively analyzed. All masses were ≤ 1.0 cm in diameter. Ultrasonic features that were analyzed included the shape, aspect ratio, boundary, margin, echo, uniformity, presence or absence of microcalcification and enlargement of the lymph nodes, as well as the blood flow of the nodules. Furthermore, the sensitivity, specificity and accuracy of ultrasonography for the diagnosis of PTMC were obtained. The following ultrasonic features of thyroid nodules were significantly (P<0.05) associated with PTMC coexisting with a thyroid abnormality: An irregular shape; an aspect ratio of ≥ 1; an unclear boundary; blurred margins; internal heterogeneous hypoechogenicity; and microcalcification. Therefore, thyroid nodules with these ultrasonic characteristics coexisting with a thyroid abnormality may be suspected as malignant PTMC. The present study demonstrated that ultrasound-guided biopsies are necessary to prevent misdiagnosis of PTMC. The sensitivities of enlarged neck lymph nodes and abundant blood flow are so low that they may be considered as references for the differentiation of PTMC from benign nodules. PMID:27698812

  11. NUCLEAR REACTOR

    DOEpatents

    Anderson, C.R.

    1962-07-24

    A fluidized bed nuclear reactor and a method of operating such a reactor are described. In the design means are provided for flowing a liquid moderator upwardly through the center of a bed of pellets of a nentron-fissionable material at such a rate as to obtain particulate fluidization while constraining the lower pontion of the bed into a conical shape. A smooth circulation of particles rising in the center and falling at the outside of the bed is thereby established. (AEC)

  12. Spatial analysis of nuclear and cytoplasmic DNA diversity in wild sea beet (Beta vulgaris ssp. maritima) populations: do marine currents shape the genetic structure?

    PubMed

    Fievet, Virgil; Touzet, Pascal; Arnaud, Jean-François; Cuguen, Joël

    2007-05-01

    Patterns of seed dispersal in the wild sea beet (Beta vulgaris ssp. maritima) are predicted to be influenced by marine currents because populations are widely distributed along the European Atlantic coast. We investigated the potential influence of marine currents on the pattern of spatial genetic structuring in natural populations of sea beet. Populations were located along the French coasts of the Anglo-Norman gulf that features peculiar marine currents in the Channel. Thirty-three populations were sampled, among which 23 were continental and 10 were insular populations located in Jersey, Guernsey and Chausey, for a total of 1224 plants genotyped. To validate the coastal topography influence and the possibility of marine current orientated gene flow on the genetic features of sea beet populations, we assessed patterns of genetic structuring of cytoplasmic and nuclear diversity by: (i) searching for an isolation-by-distance (IBD) pattern using spatial autocorrelation tools; (ii) using the Monmonier algorithm to identify genetic boundaries in the area studied; and (iii) performing assignment tests that are based on multilocus genotype information to ascertain population membership of individuals. Our results showed a highly contrasted cytoplasmic and nuclear genetic differentiation and highlighted the peculiar situation of island populations. Beyond a classical isolation-by-distance due to short-range dispersal, genetic barriers fitting the orientation of marine currents were clearly identified. This suggests the occurrence of long-distance seed dispersal events and an asymmetrical gene flow separating the eastern and western part of the Anglo-Norman gulf.

  13. High-spin nuclear structure studies with radioactive ion beams

    SciTech Connect

    Baktash, C.

    1992-12-31

    Two important developments in the sixties, namely the advent of heavy-ion accelerators and fabrication of Ge detectors, opened the way for the experimental studies of nuclear properties at high angular momentum. Addition of a new degree of freedom, namely spin, made it possible to observe such fascinating phenomena as occurrences and coexistence of a variety of novel shapes, rise, fall and occasionally rebirth of nuclear collectivity, and disappearance of pairing correlations. Today, with the promise of development of radioactive ion beams (RIB) and construction of the third-generation Ge-detection systems (GAMMASPHERE and EUROBALL), the authors are poised to explore new and equally fascinating phenomena that have been hitherto inaccessible. With the addition of yet another dimension, namely the isospin, they will be able to observe and verify predictions for exotic shapes as varied as rigid triaxiality, hyperdeformation and triaxial octupole shapes, or to investigate the T = 0 pairing correlations. In this paper, they shall review, separately for neutron-deficient and neutron-rich nuclei, these and a few other new high-spin physics opportunities that may be realized with RIB. Following this discussion, they shall present a list of the beam species, intensities and energies that are needed to fulfill these goals. The paper will conclude with a description of the experimental techniques and instrumentations that are required for these studies.

  14. Nuclear shape phase transition within a conjunction of γ-rigid and γ-stable collective behaviors in deformation-dependent mass formalism

    NASA Astrophysics Data System (ADS)

    Chabab, M.; El Batoul, A.; Lahbas, A.; Oulne, M.

    2016-12-01

    In this paper, we present a theoretical study of a conjunction of γ-rigid and γ-stable collective motions in critical point symmetries of the phase transitions from spherical to deformed shapes of nuclei using an exactly separable version of the Bohr Hamiltonian with a deformation-dependent mass term. The deformation-dependent mass is applied simultaneously to γ-rigid and γ-stable parts of this famous collective Hamiltonian. Moreover, the β part of the problem is described by means of Davidson potential, while the γ-angular part corresponding to axially symmetric shapes is treated by a harmonic oscillator potential. The energy eigenvalues and normalized eigenfunctions of the problem are obtained in compact forms by making use of the asymptotic iteration method. The combined effect of the deformation-dependent mass and rigidity as well as harmonic oscillator stiffness parameters on the energy spectrum and wave functions is duly investigated. Also, the electric quadrupole transition ratios and energy spectrum of some γ-stable and prolate nuclei are calculated and compared with the experimental data as well as with other theoretical models.

  15. Transition, coexistence, and interaction of vector localized waves arising from higher-order effects

    SciTech Connect

    Liu, Chong; Yang, Zhan-Ying; Zhao, Li-Chen; Yang, Wen-Li

    2015-11-15

    We study vector localized waves on continuous wave background with higher-order effects in a two-mode optical fiber. The striking properties of transition, coexistence, and interaction of these localized waves arising from higher-order effects are revealed in combination with corresponding modulation instability (MI) characteristics. It shows that these vector localized wave properties have no analogues in the case without higher-order effects. Specifically, compared to the scalar case, an intriguing transition between bright–dark rogue waves and w-shaped–anti-w-shaped solitons, which occurs as a result of the attenuation of MI growth rate to vanishing in the zero-frequency perturbation region, is exhibited with the relative background frequency. In particular, our results show that the w-shaped–anti-w-shaped solitons can coexist with breathers, coinciding with the MI analysis where the coexistence condition is a mixture of a modulation stability and MI region. It is interesting that their interaction is inelastic and describes a fusion process. In addition, we demonstrate an annihilation phenomenon for the interaction of two w-shaped solitons which is identified essentially as an inelastic collision in this system. -- Highlights: •Vector rogue wave properties induced by higher-order effects are studied. •A transition between vector rogue waves and solitons is obtained. •The link between the transition and modulation instability (MI) is demonstrated. •The coexistence of vector solitons and breathers coincides with the MI features. •An annihilation phenomenon for the vector two w-shaped solitons is presented.

  16. Co-existence of agricultural production systems.

    PubMed

    Jank, Bernhard; Rath, Johannes; Gaugitsch, Helmut

    2006-05-01

    Strategies and best practices for the co-existence of GM and non-GM crops need to be developed and implemented with the participation of farmers and other stakeholders. According to the principle of 'subsidiarity', decisions should be made by the lowest authority possible. When applying this concept to the case of GM crops, the affected society should determine their use and management in a regional decision-making process. Public participation is better accomplished at a lower level, and democratic deficits in decision-making on GMOs are better resolved, enabling farmers to manage or avoid GM crops. Ultimately, voluntary GMO-free zones might be a tool for sustainable co-existence and GM-free production and GMO-free zones might create a specific image for marketing regional products and services, such as tourism.

  17. Coexistence of Fabry Disease and Membranous Nephropathy.

    PubMed

    Liu, Ying; Xie, Hua; Lin, Hongli; Chen, Shuni; Wang, Weidong; Zhao, Guangben; Zhang, Xu

    2016-01-01

    A 21-year-old man with no family history or characteristic symptoms of Fabry disease presented with proteinuria. Histological and immunofluorescent analysis of kidney tissue collected revealed stage 1 membranous nephropathy. Electron microscopy of the same tissue revealed a large number of myeloid bodies (zebra bodies) in the glomerular epithelial cytoplasm and a mild irregular thickening of basement membrane. A diagnosis of Fabry disease was supported by the low α-galactosidase A activity detected in the patient's plasma, and confirmed by the detection of a pathogenic homozygous mutation in the α-galactosidase A gene. Therefore, the final diagnosis was of coexistent Fabry disease and stage 1 membranous nephropathy. This is the first case study reporting the coexistence of Fabry disease and membranous nephropathy. Our results emphasize the importance of electron microscopy in Fabry disease diagnosis.

  18. Year-class coexistence in biennial plants.

    PubMed

    Kisdi, Éva

    2012-08-01

    I extend the well known and biologically well motivated Skellam model of plant population dynamics to biennial plants. The model has two attractors: either one year class competitively excludes the other, resulting in 2-cycles with only vegetative vs only flowering plants in alternating years, or the two year classes coexist at an interior equilibrium. Contrary to earlier models, these two attractors can exist also simultaneously. I investigate the robustness of the model by including delayed flowering, a common phenomenon in plants, and provide a full numerical bifurcation analysis of the generalized model. High fecundity implies strong competition within year classes and promotes coexistence, whereas high survival results in strong competition between year classes and promotes competitive exclusion. Delayed flowering tends to stabilize the interior equilibrium, but (unlike in density-independent matrix models) the population cycles are robust with respect to some delay in flowering.

  19. Physical properties, structure, and shape of radioactive Cs from the Fukushima Daiichi Nuclear Power Plant accident derived from soil, bamboo and shiitake mushroom measurements.

    PubMed

    Niimura, Nobuo; Kikuchi, Kenji; Tuyen, Ninh Duc; Komatsuzaki, Masakazu; Motohashi, Yoshinobu

    2015-01-01

    We conducted an elution experiment with contaminated soils using various aqueous reagent solutions and autoradiography measurements of contaminated bamboo shoots and shiitake mushrooms to determine the physical and chemical characteristics of radioactive Cs from the Fukushima Daiichi Nuclear Power Plant accident. Based on our study results and data in the literature, we conclude that the active Cs emitted by the accident fell to the ground as granular non-ionic materials. Therefore, they were not adsorbed or trapped by minerals in the soil, but instead physically adhere to the rough surfaces of the soil mineral particles. Granular Cs* can be transferred among media, such as soils and plants. The physical properties and dynamic behavior of the granular Cs* is expected to be helpful in considering methods for decontamination of soil, litter, and other media.

  20. Species coexistence in a changing world.

    PubMed

    Valladares, Fernando; Bastias, Cristina C; Godoy, Oscar; Granda, Elena; Escudero, Adrián

    2015-01-01

    The consequences of global change for the maintenance of species diversity will depend on the sum of each species responses to the environment and on the interactions among them. A wide ecological literature supports that these species-specific responses can arise from factors related to life strategies, evolutionary history and intraspecific variation, and also from environmental variation in space and time. In the light of recent advances from coexistence theory combined with mechanistic explanations of diversity maintenance, we discuss how global change drivers can influence species coexistence. We revise the importance of both competition and facilitation for understanding coexistence in different ecosystems, address the influence of phylogenetic relatedness, functional traits, phenotypic plasticity and intraspecific variability, and discuss lessons learnt from invasion ecology. While most previous studies have focused their efforts on disentangling the mechanisms that maintain the biological diversity in species-rich ecosystems such as tropical forests, grasslands and coral reefs, we argue that much can be learnt from pauci-specific communities where functional variability within each species, together with demographic and stochastic processes becomes key to understand species interactions and eventually community responses to global change.

  1. Species coexistence in a changing world

    PubMed Central

    Valladares, Fernando; Bastias, Cristina C.; Godoy, Oscar; Granda, Elena; Escudero, Adrián

    2015-01-01

    The consequences of global change for the maintenance of species diversity will depend on the sum of each species responses to the environment and on the interactions among them. A wide ecological literature supports that these species-specific responses can arise from factors related to life strategies, evolutionary history and intraspecific variation, and also from environmental variation in space and time. In the light of recent advances from coexistence theory combined with mechanistic explanations of diversity maintenance, we discuss how global change drivers can influence species coexistence. We revise the importance of both competition and facilitation for understanding coexistence in different ecosystems, address the influence of phylogenetic relatedness, functional traits, phenotypic plasticity and intraspecific variability, and discuss lessons learnt from invasion ecology. While most previous studies have focused their efforts on disentangling the mechanisms that maintain the biological diversity in species-rich ecosystems such as tropical forests, grasslands and coral reefs, we argue that much can be learnt from pauci-specific communities where functional variability within each species, together with demographic and stochastic processes becomes key to understand species interactions and eventually community responses to global change. PMID:26528323

  2. Body Size Mediated Coexistence in Swans

    PubMed Central

    Engelhardt, Katharina A. M.; Ritchie, Mark E.; Powell, James A.

    2014-01-01

    Differences in body sizes may create a trade-off between foraging efficiency (foraging gains/costs) and access to resources. Such a trade-off provides a potential mechanism for ecologically similar species to coexist on one resource. We explored this hypothesis for tundra (Cygnus columbianus) and trumpeter swans (Cygnus buccinator), a federally protected species, feeding solely on sago pondweed (Stuckenia pectinata) tubers during fall staging and wintering in northern Utah. Foraging efficiency was higher for tundra swans because this species experienced lower foraging and metabolic costs relative to foraging gains; however, trumpeter swans (a) had longer necks and therefore had access to exclusive resources buried deep in wetland sediments and (b) were more aggressive and could therefore displace tundra swans from lucrative foraging locations. We conclude that body size differentiation is an important feature of coexistence among ecologically similar species feeding on one resource. In situations where resources are limiting and competition for resources is strong, conservation managers will need to consider the trade-off between foraging efficiency and access to resources to ensure ecologically similar species can coexist on a shared resource. PMID:24672347

  3. Emergent neutrality drives phytoplankton species coexistence

    PubMed Central

    Segura, Angel M.; Calliari, Danilo; Kruk, Carla; Conde, Daniel; Bonilla, Sylvia; Fort, Hugo

    2011-01-01

    The mechanisms that drive species coexistence and community dynamics have long puzzled ecologists. Here, we explain species coexistence, size structure and diversity patterns in a phytoplankton community using a combination of four fundamental factors: organism traits, size-based constraints, hydrology and species competition. Using a ‘microscopic’ Lotka–Volterra competition (MLVC) model (i.e. with explicit recipes to compute its parameters), we provide a mechanistic explanation of species coexistence along a niche axis (i.e. organismic volume). We based our model on empirically measured quantities, minimal ecological assumptions and stochastic processes. In nature, we found aggregated patterns of species biovolume (i.e. clumps) along the volume axis and a peak in species richness. Both patterns were reproduced by the MLVC model. Observed clumps corresponded to niche zones (volumes) where species fitness was highest, or where fitness was equal among competing species. The latter implies the action of equalizing processes, which would suggest emergent neutrality as a plausible mechanism to explain community patterns. PMID:21177680

  4. d{sub 5/2} proton hole strength in neutron-rich {sup 43}P: Shell structure and nuclear shapes near N=28

    SciTech Connect

    Riley, L. A.; Baugher, T. R.; Hosier, K. E.; Adrich, P.; Bazin, D.; Diget, C. A.; Weisshaar, D.; Brown, B. A.; Cook, J. M.; Gade, A.; Garland, D. A.; Glasmacher, T.; Ratkiewicz, A.; Siwek, K. P.; Cottle, P. D.; Kemper, K. W.; Otsuka, T.; Rae, W. D. M.; Tostevin, J. A.; Utsuno, Y.

    2008-07-15

    We report on the use of the one-proton knockout reaction from {sup 44}S to determine the location of d{sub 5/2} proton strength in neutron-rich {sup 43}P. The results are used to test two shell-model frameworks with different pictures of the evolution of single-proton energies along the N=28 isotones near the neutron dripline. We observe a concentration of d{sub 5/2} proton hole strength near 1 MeV in excitation energy. This result favors the recent shell-model interaction of Utsuno et al. [Eur. Phys. J. Spec. Top. 150, 187 (2007)] and provides additional evidence for an oblate shape for {sup 42}Si.

  5. Revisiting the Two-Layer Hypothesis: Coexistence of Alternative Functional Rooting Strategies in Savannas

    PubMed Central

    Holdo, Ricardo M.

    2013-01-01

    The two-layer hypothesis of tree-grass coexistence posits that trees and grasses differ in rooting depth, with grasses exploiting soil moisture in shallow layers while trees have exclusive access to deep water. The lack of clear differences in maximum rooting depth between these two functional groups, however, has caused this model to fall out of favor. The alternative model, the demographic bottleneck hypothesis, suggests that trees and grasses occupy overlapping rooting niches, and that stochastic events such as fires and droughts result in episodic tree mortality at various life stages, thus preventing trees from otherwise displacing grasses, at least in mesic savannas. Two potential problems with this view are: 1) we lack data on functional rooting profiles in trees and grasses, and these profiles are not necessarily reflected by differences in maximum or physical rooting depth, and 2) subtle, difficult-to-detect differences in rooting profiles between the two functional groups may be sufficient to result in coexistence in many situations. To tackle this question, I coupled a plant uptake model with a soil moisture dynamics model to explore the environmental conditions under which functional rooting profiles with equal rooting depth but different depth distributions (i.e., shapes) can coexist when competing for water. I show that, as long as rainfall inputs are stochastic, coexistence based on rooting differences is viable under a wide range of conditions, even when these differences are subtle. The results also indicate that coexistence mechanisms based on rooting niche differentiation are more viable under some climatic and edaphic conditions than others. This suggests that the two-layer model is both viable and stochastic in nature, and that a full understanding of tree-grass coexistence and dynamics may require incorporating fine-scale rooting differences between these functional groups and realistic stochastic climate drivers into future models. PMID

  6. The role of Pleistocene glaciations in shaping the evolution of polar and brown bears. Evidence from a critical review of mitochondrial and nuclear genome analyses.

    PubMed

    Hassanin, Alexandre

    2015-07-01

    In this report, I review recent molecular studies dealing with the origin and evolution of polar bears (Ursus maritimus), with special emphasis on their relationships with brown bears (U. arctos). On the basis of mitochondrial and nuclear data, different hypotheses have been proposed, including rapid morphological differentiation of U. maritimus, genetic introgression from U. arctos into U. maritimus, or inversely from U. maritimus into U. arctos, involving either male- or female-mediated gene flow. In the light of available molecular and eco-ethological data, I suggest, firstly, that all divergences among major clades of large bears can be linked to glacial periods, secondly, that polar bears diverged from brown bears before 530 thousand years ago (ka), during one of the three glacial marine isotope stages (MIS) 14, 15.2 or 16, and, thirdly, that genetic introgression had occurred from female polar bears into brown bear populations during at least two glacial periods, at 340 ± 10 ka (MIS 10) in western Europe, and at 155 ± 5 ka (MIS 6) on the ABC islands of southeastern Alaska, and probably also in Beringia and Ireland based on ancient DNA sequences. Copyright © 2015 Académie des sciences. Published by Elsevier SAS. All rights reserved.

  7. Unusual coexistence of extramedullary plasmacytoma and nasopharyngeal carcinoma in nasopharynx.

    PubMed

    Du, Ri-Chang; Li, Hai-Nan; Huang, Wei; Tian, Xiao-Ying; Li, Zhi

    2015-09-17

    Nasopharyngeal carcinoma (NPC) is an EBV-associated malignant tumor of nasopharynx. As extremely rare condition, the second primary cancer of nasopharynx can occur in NPC patients synchronously or subsequently. Extramedullary plasmacytoma (EMP) is a rare tumor and commonly originates in the head and neck region. However, there is no report to describe a collision tumor of NPC and EMP occurring in the same nasopharyngeal mass. We report here an unusual case of synchronous coexistence of NPC and EMP occurring in the nasopharynx of an old male patient. A 63-year-old male patient presented with a 3-month history of right-sided nasal obstruction and recently intermittent epistaxis without enlargement of cervical lymph nodes. The solitary mass of nasopharynx was found by radiological and nasopharyngeal examination. Histologically, the mass contained two separated portions and displayed typically histological features of NPC and EMP, respectively. In EMP portion, the tumor was composed of monomorphic plasmacytoid-appearing cells with immuno-positive to CD79a, CD138, CD38, MUM-1 and CD56, but lack immunoreactivity to pan-CK (AE1/AE3), CD20, CD21 and EBERs. In NPC portion, the tumor cells formed irregular-shaped islands with diffusely immuno-positive to pan-CK (AE1/AE3), EMA and EBERs, but lack expressions of lymphoplasmacytic markers. A diagnosis of simultaneous occurrence of EMP and NPC in nasopharynx was made. There was no evidence of tumor recurrence or metastasis 18-month follow-up after radiotherapy. To our knowledge, it may be the first case of coexistence of EMP and NPC synchronously. In addition, the histological differential diagnosis and relevant potential mechanism of this unusual collision tumor were also discussed.

  8. Two Types of Coexistence in Cross-Feeding Microbial Consortia

    NASA Astrophysics Data System (ADS)

    Nakaoka, Shinji; Takeuchi, Yasuhiro

    2008-07-01

    Exploitative competition of two cross-feeding strains is studied. We found that two types of coexistence of two cross-feeding strains, type-I coexistence (cultivated type) and type-II coexistence (self-sufficiency type) are possible for microbial cross-feeding strains. In all cases of coexistence, trade-off in nutrient availability is required. However, trade-off is necessary but is not sufficient for the coexistence of two strains. Over-production of metabolite can induce competitive exclusion on one hand (cultivated regime) whereas do support the coexistence of two strain on the other hand (self-sufficiency regime). Coexistence of two strains is evaluated by invasibility and permanence criteria and numerical simulations.

  9. Local coexistence and genetic isolation of three pollinator species on the same fig tree species.

    PubMed

    Sutton, T L; DeGabriel, J L; Riegler, M; Cook, J M

    2017-01-11

    Molecular tools increasingly reveal cryptic lineages and species that were previously unnoticed by traditional taxonomy. The discovery of cryptic species in sympatry prompts the question of how they coexist in the apparent absence of ecological divergence. However, this assumes first that the molecular taxonomy used to identify cryptic lineages delimits species boundaries accurately. This issue is important, because many diversity studies rely heavily or solely on data from mitochondrial DNA sequences for species delimitation, and several factors may lead to poor identification of species boundaries. We used a multilocus population genetics approach to show that three mtDNA-defined cryptic lineages of the fig wasp Pleistodontes imperialis Saunders, which pollinate Port Jackson figs (Ficus rubiginosa) in north-eastern Australia, represent reproductively isolated species. These species coexist locally, with about 13% of figs (where mating occurs) containing wasps from two or three species. However, there was no evidence for gene flow between them. Confirmed cases of coexisting cryptic species provide excellent opportunities for future studies of the ecological and evolutionary forces shaping both species coexistence and fig/pollinator coevolution.Heredity advance online publication, 11 January 2017; doi:10.1038/hdy.2016.125.

  10. Measurements of the Coexistence Curve near the Liquid-Gas Critical Point

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob

    2003-01-01

    The shape of the liquid-gas coexistence curve of He-3 very near the critical point (-2x10(exp -6) < t < -5x10(exp -3) was measured using the quasi-static thermogram method. The study was performed in Earth s gravitational field using two different height calorimetry cells, both originally designed for simultaneous measurements of the isochoric heat capacity, isothermal compressibility, and PVT. The heights of two cells were 0.5 mm and 4.8 cm. The uncertainty in measuring the phase transition temperature was typically +/-2 micro-K. The measured coexistence curve near the critical point was strongly affected by the gravitational field. Away from the critical point, the coexistence curve obtained using this technique was also consistent with the earlier work using the local density measurements of Pittman et al. The recent crossover parametric model of the equation-of-state are used to analyze the height-dependent measured coexistence curves. Data analyses have indicated that microgravity will permit measurements within two additional decades in reduced temperatures beyond the best gravity-free data obtained in Earth-bound experiments.

  11. Plant-mycorrhizal interactions mediate plant community coexistence by altering resource demand.

    PubMed

    Jiang, Jiang; Moore, Jessica A M; Priyadarshi, Anupam; Classen, Aimée T

    2017-01-01

    As the diversity of plants increases in an ecosystem, so does resource competition for soil nutrients, a process that mycorrhizal fungi can mediate. The influence of mycorrhizal fungi on plant biodiversity likely depends on the strength of the symbiosis between the plant and fungi, the differential plant growth responses to mycorrhizal inoculation, and the transfer rate of nutrients from the fungus to plant. However, our current understanding of how nutrient-plant-mycorrhizal interactions influence plant coexistence is conceptual and thus lacks a unified quantitative framework. To quantify the conditions of plant coexistence mediated by mycorrhizal fungi, we developed a mechanistic resource competition model that explicitly included plant-mycorrhizal symbioses. We found that plant-mycorrhizal interactions shape plant coexistence patterns by creating a tradeoff in resource competition. Especially, a tradeoff in resource competition was caused by differential payback in the carbon resources that plants invested in the fungal symbiosis and/or by the stoichiometric constraints on plants that required additional, less-beneficial, resources to sustain growth. Our results suggested that resource availability and the variation in plant-mycorrhizal interactions act in concert to drive plant coexistence patterns. Applying our framework, future empirical studies should investigate plant-mycorrhizal interactions under multiple levels of resource availability. © 2016 by the Ecological Society of America.

  12. Measurements of the Coexistence Curve near the Liquid-Gas Critical Point

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob

    2003-01-01

    The shape of the liquid-gas coexistence curve of He-3 very near the critical point (-2x10(exp -6) < t < -5x10(exp -3) was measured using the quasi-static thermogram method. The study was performed in Earth s gravitational field using two different height calorimetry cells, both originally designed for simultaneous measurements of the isochoric heat capacity, isothermal compressibility, and PVT. The heights of two cells were 0.5 mm and 4.8 cm. The uncertainty in measuring the phase transition temperature was typically +/-2 micro-K. The measured coexistence curve near the critical point was strongly affected by the gravitational field. Away from the critical point, the coexistence curve obtained using this technique was also consistent with the earlier work using the local density measurements of Pittman et al. The recent crossover parametric model of the equation-of-state are used to analyze the height-dependent measured coexistence curves. Data analyses have indicated that microgravity will permit measurements within two additional decades in reduced temperatures beyond the best gravity-free data obtained in Earth-bound experiments.

  13. Coexistence of Sarcoidosis and Gouty Arthritis.

    PubMed

    Semiz, Hüseyin; Kobak, Senol

    2017-08-21

    Sarcoidosis is an inflammatory disease with unknown cause characterized by non-caseating granuloma formations. It may present with bilateral hilar lymphadenopathy, skin lesions, the involvement of eye and symptoms on the locomotor system. Gouty arthritis is an autoinflammatory disease characterized by hyperuricemia, recurrent arthritis attacks and the deposition of monosodium urate crystals in the joints and the surrounding tissues. We reported the coexistence of sarcoidosis and gouty arthritis in this paper. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Reumatología y Colegio Mexicano de Reumatología. All rights reserved.

  14. Interfaces in coexisting metals and Mott insulators

    NASA Astrophysics Data System (ADS)

    Lee, Juho; Yee, Chuck-Hou

    2017-05-01

    Motivated by the direct observation of electronic phase separation in first-order Mott transitions, we model the interface between thermodynamically coexisting metals and Mott insulators. We show how to model the required slab geometry and extract the electronic spectra. We construct an effective Landau free energy and compute the variation of its parameters across the phase diagram. Finally, using a linear mixture of the density and double occupancy, we identify a natural Ising order parameter which unifies the treatment of the bandwidth and filling controlled Mott transitions.

  15. Composite bulges: the coexistence of classical bulges and discy pseudo-bulges in S0 and spiral galaxies

    NASA Astrophysics Data System (ADS)

    Erwin, Peter; Saglia, Roberto P.; Fabricius, Maximilian; Thomas, Jens; Nowak, Nina; Rusli, Stephanie; Bender, Ralf; Vega Beltrán, Juan Carlos; Beckman, John E.

    2015-02-01

    We present an analysis of nine S0-Sb galaxies which have (photometric) bulges consisting of two distinct components. The outer component is a flattened, kinematically cool, disc-like structure: a `discy pseudo-bulge'. Embedded inside is a rounder, kinematically hot spheroidal structure: a `classical bulge'. This indicates that pseudo-bulges and classical bulges are not mutually exclusive phenomena: some galaxies have both. The discy pseudo-bulges almost always consist of an exponential disc (scalelengths = 125-870 pc, mean size ˜440 pc) with one or more disc-related subcomponents: nuclear rings, nuclear bars, and/or spiral arms. They constitute 11-59 per cent of the galaxy stellar mass (mean PB/T = 0.33), with stellar masses ˜7 × 109-9 × 1010 M⊙. The classical-bulge components have Sérsic indices of 0.9-2.2, effective radii of 25-430 pc and stellar masses of 5 × 108-3 × 1010 M⊙; they are usually <10 per cent of the galaxy's stellar mass (mean B/T = 0.06). The classical bulges do show rotation, but are clearly kinematically hotter than the discy pseudo-bulges. Dynamical modelling of three systems indicates that velocity dispersions are isotropic in the classical bulges and equatorially biased in the discy pseudo-bulges. In the mass-radius and mass-stellar mass density planes, classical-bulge components follow sequences defined by ellipticals and (larger) classical bulges. Discy pseudo-bulges also fall on this sequence; they are more compact than large-scale discs of similar mass. Although some classical bulges are quite compact, they are as a class clearly distinct from nuclear star clusters in both size and mass; in at least two galaxies they coexist with nuclear clusters. Since almost all the galaxies in this study are barred, they probably also host boxy/peanut-shaped bulges (vertically thickened inner parts of bars). NGC 3368 shows isophotal evidence for such a zone just outside its discy pseudo-bulge, making it a clear case of a galaxy with all three

  16. Agammaglobulinaemia and co-existent pernicious anaemia

    PubMed Central

    Douglas, S. D.; Goldberg, L. S.; Fudenberg, H. H.; Goldberg, S. B.

    1970-01-01

    Immunological studies were performed on a woman with agammaglobulinaemia and coexistent pernicious anaemia, on her two daughters who had recurrent sinusitis, and on her husband. Serum levels of IgG, IgA and IgM were markedly reduced in the patient, whereas both daughters had a marked selective deficiency of IgA. Autoantibodies to intrinsic factor and to the gastric parietal cell were absent in these subjects, but the serum of one daughter contained thyroid autoantibodies. Assessment of the in vitro response of lymphocytes to four phytomitogens (phytohaemagglutinin, pokeweed, wax-bean and Concanavalin A) showed an altered response to Concanavalin A and an essentially normal response profile to the other mitogens. These responses differed significantly from those of eight agammaglobulinaemic patients without coexistent autoimmune disease, suggesting that subtle immune differences may exist between these two groups of patients. The findings suggest that at least three immunological aberrations in this family were under genetic control; these included abnormalities in serum immunoglobulin levels, altered in vitro lymphocyte response to Concanavalin A and an autoimmune concomitant of pernicious anaemia. PMID:5435714

  17. Coexistence of papillary carcinoma and Hashimoto's thyroiditis.

    PubMed

    Matesa-Anić, Dubravka; Matesa, Neven; Dabelić, Nina; Kusić, Zvonko

    2009-03-01

    The aim of the study was to determine the incidence of coexistence of papillary carcinoma and Hashimoto's thyroiditis in cytologic material. Cytologic findings were collected from 10508 patients that underwent ultrasound-guided fine needle aspiration cytology (FNAC) of the thyroid. Hashimoto's thyroiditis was found in 2156 (20.5%) and papillary carcinoma in 269 (2.6%) of 10508 patients with FNAC, whereas both Hashimoto's thyroiditis and papillary carcinoma were present in 42 (0.4%) patients. Among patients with FNAC diagnosis of Hashimoto's thyroiditis, the prevalence of papillary carcinoma was 1.9%. Among patients with FNAC diagnosis of papillary carcinoma, the prevalence of Hashimoto's thyroiditis was 15.6%. There was no statistically significant association between the presence of papillary carcinoma and Hashimoto's thyroiditis in patients undergoing FNAC (p=0.0522). In conclusion, in a large series of patients, the incidence of Hashimoto's thyroiditis and papillary carcinoma coexistence in cytologic material was 0.4%. There was no statistically significant relationship between Hashimoto's thyroiditis and papillary carcinoma in cytologic material.

  18. Coexistence Curve of Perfluoromethylcyclohexane-Isopropyl Alcohol

    NASA Technical Reports Server (NTRS)

    Jacobs, D. T.; Kuhl, D. E.; Selby, C. E.

    1996-01-01

    The coexistence curve of the binary fluid mixture perfluoromethylcyclohexane-isopropyl alcohol was determined by precisely measuring the refractive index both above and below its upper critical consolute point. Sixty-seven two-phase data points were obtained over a wide range of reduced temperatures, 10(exp -5) less than t less than 2.5 x 10(exp -1), to determine the location of the critical point: critical temperature=89.901 C, and critical composition = 62.2% by volume perfluoromethylcyclohexane. These data were analyzed to determine the critical exponent 8 close to the critical point, the amplitude B, and the anomaly in the diameter. The volume-fraction coexistence curve is found to be as symmetric as any composition like variable. Correction to scaling is investigated as well as the need for a crossover theory. A model is proposed that describes the asymptotic approach to zero of the effective exponent Beta, which allows an estimation of the temperature regime free of crossover effects.

  19. Congenital glioblastoma coexisting with vascular developmental anomaly.

    PubMed

    Laure-Kamionowska, Milena; Szymanska, Krystyna; Biekiesinska-Figatowska, Monika; Gierowska-Bogusz, Barbara; Michalak, Elżbieta; Klepacka, Teresa

    2013-01-01

    Congenital central nervous tumours form a unique group of neoplasms. They are different from other tumour groups not only due to the onset time but also to their histopathology, anatomic location, and biologic behaviour. Congenital glioblastoma is one of the rarest types of congenital brain tumours and is uncommon in the prenatal period. We report a rare case of congenital glioblastoma detected prenatally by ultrasound examination and magnetic resonance imaging at 26 gestational weeks. Based on MRI findings and consultation of a team of specialists, pregnancy was terminated at 28 weeks. The newborn presented hydrops foetal. The child died shortly after birth due to cardiorespiratory insufficiency. At autopsy a large tumour with a spongy-like appearance was found. The tumour involved nearly the whole right cerebral hemisphere and led to marked hydrocephalus. In the histological and immunohistochemical examination, the tumour presented features of glioblastoma. Neoplastic cells were immunopositive for GFAP, S-100 protein and negative for neuronal markers. Frequent mitoses and high MIB-1 labelling index were seen in the tumour areas. The coexistence of tumour and vascular developmental anomaly was stated. The conglomerates of numerous, distended, thin-walled foetal-like blood vessels were located beside the tumour tissue, which presented disturbance in differentiation and maturation of the vascular net. Such coexistence of malignant glioma with vascular developmental anomaly is unique.

  20. China and the global uranium market: prospects for peaceful coexistence.

    PubMed

    Massot, Pascale; Chen, Zhan-Ming

    2013-01-01

    China's recent reemergence has resulted in a significant increase in the global demand of commodities and is already having major impacts on the dynamics of global commodity markets. In the case of the global uranium market, we stand at the very beginning of a period of change. However, interesting trends are already emerging. Whereas China has had many policy reversals, and some difficulties in taking control of its procurement strategy in other commodity markets, it is seemingly more successful in managing its uranium procurement strategy. Why? The argument presented here is that a mixture of domestic and international level variables has allowed China more room for maneuver in fulfilling its uranium procurement strategy. On the domestic level, a centralized industry, and, on the international level, a geographically dispersed and uncoordinated market have allowed China to forge ahead with an ambitious civilian nuclear power plan and triple its total uranium imports, all within the span of a few years. Many challenges remain, not the least that of negative public opinion, which has surged since the Fukushima disaster in 2011. Nevertheless, should uranium demand continue to grow, this paper will consider the potential for continued peaceful coexistence among uranium market participants worldwide.

  1. China and the Global Uranium Market: Prospects for Peaceful Coexistence

    PubMed Central

    Massot, Pascale

    2013-01-01

    China's recent reemergence has resulted in a significant increase in the global demand of commodities and is already having major impacts on the dynamics of global commodity markets. In the case of the global uranium market, we stand at the very beginning of a period of change. However, interesting trends are already emerging. Whereas China has had many policy reversals, and some difficulties in taking control of its procurement strategy in other commodity markets, it is seemingly more successful in managing its uranium procurement strategy. Why? The argument presented here is that a mixture of domestic and international level variables has allowed China more room for maneuver in fulfilling its uranium procurement strategy. On the domestic level, a centralized industry, and, on the international level, a geographically dispersed and uncoordinated market have allowed China to forge ahead with an ambitious civilian nuclear power plan and triple its total uranium imports, all within the span of a few years. Many challenges remain, not the least that of negative public opinion, which has surged since the Fukushima disaster in 2011. Nevertheless, should uranium demand continue to grow, this paper will consider the potential for continued peaceful coexistence among uranium market participants worldwide. PMID:23606818

  2. Nuclear physics

    SciTech Connect

    Garg, U.; Reviol, W.; Kaczarowski, R.

    1995-08-01

    Several groups from the University of Notre Dame are playing an important role in developing the research program at ATLAS. One of their main interests is the study, in collaboration with ANL staff members, of the behavior of nuclei at high spin in the transitional region near A=180 (i.e. the Hg-Pt-Os nuclei), and A=100 (i.e. the Ru-Tc nuclei) with emphasis on shape coexistence and configuration mixing. This group has also participated in many other experiments performed with the BGO gamma-ray facility, especially in the investigation of superdeformation. The {gamma}-ray groups at ANL and Notre Dame have also had collaborative experiments at Gammasphere. The Notre Dame group has built, tested and extensively used a state-of-the-art plunger device for lifetime measurements in conjunction with the ATLAS {gamma}-ray facility. An adapted version of this device is now under construction at Notre Dame, under contract with ANL, for use at the Gammasphere facility.

  3. Multiple Coexisting Dirac Surface States in Three-Dimensional Topological Insulator PbBi₆Te₁₀.

    PubMed

    Papagno, Marco; Eremeev, Sergey V; Fujii, Jun; Aliev, Ziya S; Babanly, Mahammad B; Mahatha, Sanjoy Kr; Vobornik, Ivana; Mamedov, Nazim T; Pacilé, Daniela; Chulkov, Evgueni V

    2016-03-22

    By means of angle-resolved photoemission spectroscopy (ARPES) measurements, we unveil the electronic band structure of three-dimensional PbBi6Te10 topological insulator. ARPES investigations evidence multiple coexisting Dirac surface states at the zone-center of the reciprocal space, displaying distinct electronic band dispersion, different constant energy contours, and Dirac point energies. We also provide evidence of Rashba-like split states close to the Fermi level, and deeper M- and V-shaped bands coexisting with the topological surface states. The experimental findings are in agreement with scanning tunneling microscopy measurements revealing different surface terminations according to the crystal structure of PbBi6Te10. Our experimental results are supported by density functional theory calculations predicting multiple topological surface states according to different surface cleavage planes.

  4. Stoichiometry is crucial for modelling phytoplankton coexistence

    NASA Astrophysics Data System (ADS)

    Göthlich, Lena; Oschlies, Andreas

    2010-05-01

    each of these species. A model study is presented in which the stability conditions for the aforementioned equilibrium are evaluated. The conditions for stable coexistence in a chemostat derived by Huisman and Weissing (J Huisman & F Weissing, Ecology 2001, Vol 82(10), pp 2682-2695) imply that the species' stoichiometries need to differ from one another. In this study, it is shown both numerically and analytically that, given each species is limited by a different resource, stable coexistence is still not possible if all species are assigned the same stoichiometry. This collides with the widely applied Redfield stoichiometry, which is routinely applied in phytoplankton models. Thus, to sustain coexistence in plankton models, it is not only necessary to parameterise the resource requirements according to the R* concept, but to also vary the stoichiometric coefficients across the species involved.

  5. The Lion King and the Hyaena Queen: large carnivore interactions and coexistence.

    PubMed

    Périquet, Stéphanie; Fritz, Hervé; Revilla, Eloy

    2015-11-01

    Interactions among species, which range from competition to facilitation, have profound effects on ecosystem functioning. Large carnivores are of particular importance in shaping community structure since they are at the top of the food chain, and many efforts are made to conserve such keystone species. Despite this, the mechanisms of carnivore interactions are far from understood, yet they are key to enabling or hindering their coexistence and hence are highly relevant for their conservation. The goal of this review is thus to provide detailed information on the extents of competition and facilitation between large carnivores and their impact in shaping their life histories. Here, we use the example of spotted hyaenas (Crocuta crocuta) and lions (Panthera leo) and provide a comprehensive knowledge of their interactions based on meta-analyses from available literature (148 publications). Despite their strong potential for both exploitation and interference competition (range and diet overlap, intraguild predation and kleptoparasitism), we underline some mechanisms facilitating their coexistence (different prey-age selection and scavenging opportunities). We stress the fact that prey abundance is key to their coexistence and that hyaenas forming very large groups in rich ecosystems could have a negative impact on lions. We show that the coexistence of spotted hyaenas and lions is a complex balance between competition and facilitation, and that prey availability within the ecosystem determines which predator is dominant. However, there are still many gaps in our knowledge such as the spatio-temporal dynamics of their interactions. As both species' survival becomes increasingly dependent on protected areas, where their densities can be high, it is critical to understand their interactions to inform both reintroduction programs and protected area management.

  6. Examining the relative importance of spatial and nonspatial coexistence mechanisms.

    PubMed

    Snyder, Robin E; Borer, Elizabeth T; Chesson, Peter

    2005-10-01

    Much of the work on species coexistence has focused on the presence or absence of single mechanisms. Most theoretical frameworks, however, do not allow one to measure the strength of coexistence mechanisms, and so it has been difficult to determine the relative importance of each mechanism when multiple mechanisms are present. We present a model inspired by the California red scale system, in which two parasitoids coexist on a single, tree-dwelling host-scale insect. Previous work suggests that coexistence may be promoted both by intraguild predation (IGP) and by differing preferences for hosts on stems versus hosts on leaves (habitat preference). By applying an analytic framework that quantifies the strengths of spatial coexistence mechanisms, we are able to measure the individual contributions of IGP, habitat preference, and their interaction to maintaining coexistence. We find that habitat preference is much more effective at promoting coexistence in this model than in IGP. Furthermore, the effects of habitat preference and IGP are not independent. When the two parasitoids prefer different habitats, the coexistence-promoting effects of habitat preference are strengthened by IGP if IGP gives a moderate advantage to the inferior competitor. If IGP either confers an excessive advantage or favors the superior competitor, it can diminish the coexistence region.

  7. Different dispersal abilities allow reef fish to coexist.

    PubMed

    Bode, Michael; Bode, Lance; Armsworth, Paul R

    2011-09-27

    The coexistence of multiple species on a smaller number of limiting resources is an enduring ecological paradox. The mechanisms that maintain such biodiversity are of great interest to ecology and of central importance to conservation. We describe and prove a unique and robust mechanism for coexistence: Species that differ only in their dispersal abilities can coexist, if habitat patches are distributed at irregular distances. This mechanism is straightforward and ecologically intuitive, but can nevertheless create complex coexistence patterns that are robust to substantial environmental stochasticity. The Great Barrier Reef (GBR) is noted for its diversity of reef fish species and its complex arrangement of reef habitat. We demonstrate that this mechanism can allow fish species with different pelagic larval durations to stably coexist in the GBR. Further, coexisting species on the GBR often dominate different subregions, defined primarily by cross-shelf position. Interspecific differences in dispersal ability generate similar coexistence patterns when dispersal is influenced by larval behavior and variable oceanographic conditions. Many marine and terrestrial ecosystems are characterized by patchy habitat distributions and contain coexisting species that have different dispersal abilities. This coexistence mechanism is therefore likely to have ecological relevance beyond reef fish.

  8. Genes and processed paralogs co-exist in plant mitochondria.

    PubMed

    Cuenca, Argelia; Petersen, Gitte; Seberg, Ole; Jahren, Anne Hoppe

    2012-04-01

    RNA-mediated gene duplication has been proposed to create processed paralogs in the plant mitochondrial genome. A processed paralog may retain signatures left by the maturation process of its RNA precursor, such as intron removal and no need of RNA editing. Whereas it is well documented that an RNA intermediary is involved in the transfer of mitochondrial genes to the nucleus, no direct evidence exists for insertion of processed paralogs in the mitochondria (i.e., processed and un-processed genes have never been found simultaneously in the mitochondrial genome). In this study, we sequenced a region of the mitochondrial gene nad1, and identified a number of taxa were two different copies of the region co-occur in the mitochondria. The two nad1 paralogs differed in their (a) presence or absence of a group II intron, and (b) number of edited sites. Thus, this work provides the first evidence of co-existence of processed paralogs and their precursors within the plant mitochondrial genome. In addition, mapping the presence/absence of the paralogs provides indirect evidence of RNA-mediated gene duplication as an essential process shaping the mitochondrial genome in plants.

  9. Thermophysical properties of coexistent phases of plutonium

    SciTech Connect

    Freibert, Franz J; Mitchell, Jeremy N; Saleh, Tarik A; Schwartz, Dan S

    2009-01-01

    Plutonium is the element with the greatest number of allotropic phases. Thermally induced transformations between these phases are typically characterized by thermal hysteresis and incomplete phase reversion. With Ga substitutal in the lattice, low symmetry phases are replaced by a higher symmetry phase. However, the low temperature Martensitic phase transformation ({delta} {yields} {alpha}{prime}) in Ga stabilized {delta}-phase Pu is characterized by a region of thermal hysteresis which can reach 200 C in extent. These regions of thermal hysteresis offer a unique opportunity to study thermodynamics in inhomogeneous systems of coexistent phases. The results of thermophysical properties measured for samples of inhomogeneous unalloyed and Ga alloyed Pu will be discussed and compared with similar measurements of their single phase constituents.

  10. Coexisting attractors in periodically modulated logistic maps.

    PubMed

    Singh, Thounaojam Umeshkanta; Nandi, Amitabha; Ramaswamy, Ram

    2008-06-01

    We consider the logistic map wherein the nonlinearity parameter is periodically modulated. For low periods, there is multistability, namely two or more distinct dynamical attractors coexist. The case of period 2 is treated in detail, and it is shown how an extension of the kneading theory for one-dimensional maps can be applied in order to analyze the origin of bistability, and to demarcate the principal regions of bistability in the phase space. When the period of the modulation is increased-and here we choose periods which are the Fibonacci numbers-the measure of multistable regions decreases. The limit of quasiperiodic driving is approached in two different ways, by increasing the period and keeping the drive dichotomous, or by increasing the period and varying the modulation sinusoidally. In the former case, we find that multistability persists in small regions of the phase space, while in the latter, there is no evidence of multistability but strange nonchaotic attractors are created.

  11. Novel trophic cascades: apex predators enable coexistence.

    PubMed

    Wallach, Arian D; Ripple, William J; Carroll, Scott P

    2015-03-01

    Novel assemblages of native and introduced species characterize a growing proportion of ecosystems worldwide. Some introduced species have contributed to extinctions, even extinction waves, spurring widespread efforts to eradicate or control them. We propose that trophic cascade theory offers insights into why introduced species sometimes become harmful, but in other cases stably coexist with natives and offer net benefits. Large predators commonly limit populations of potentially irruptive prey and mesopredators, both native and introduced. This top-down force influences a wide range of ecosystem processes that often enhance biodiversity. We argue that many species, regardless of their origin or priors, are allies for the retention and restoration of biodiversity in top-down regulated ecosystems.

  12. Emergence of coexisting percolating clusters in networks

    NASA Astrophysics Data System (ADS)

    Faqeeh, Ali; Melnik, Sergey; Colomer-de-Simón, Pol; Gleeson, James P.

    2016-06-01

    It is commonly assumed in percolation theories that at most one percolating cluster can exist in a network. We show that several coexisting percolating clusters (CPCs) can emerge in networks due to limited mixing, i.e., a finite and sufficiently small number of interlinks between network modules. We develop an approach called modular message passing (MMP) to describe and verify these observations. We demonstrate that the appearance of CPCs is an important source of inaccuracy in previously introduced percolation theories, such as the message passing (MP) approach, which is a state-of-the-art theory based on the belief propagation method. Moreover, we show that the MMP theory improves significantly over the predictions of MP for percolation on synthetic networks with limited mixing and also on several real-world networks. These findings have important implications for understanding the robustness of networks and in quantifying epidemic outbreaks in the susceptible-infected-recovered (SIR) model of disease spread.

  13. Early Mesozoic Coexistence of Amniotes and Hepadnaviridae

    PubMed Central

    Suh, Alexander; Weber, Claudia C.; Kehlmaier, Christian; Braun, Edward L.; Green, Richard E.; Fritz, Uwe; Ray, David A.; Ellegren, Hans

    2014-01-01

    Hepadnaviridae are double-stranded DNA viruses that infect some species of birds and mammals. This includes humans, where hepatitis B viruses (HBVs) are prevalent pathogens in considerable parts of the global population. Recently, endogenized sequences of HBVs (eHBVs) have been discovered in bird genomes where they constitute direct evidence for the coexistence of these viruses and their hosts from the late Mesozoic until present. Nevertheless, virtually nothing is known about the ancient host range of this virus family in other animals. Here we report the first eHBVs from crocodilian, snake, and turtle genomes, including a turtle eHBV that endogenized >207 million years ago. This genomic “fossil” is >125 million years older than the oldest avian eHBV and provides the first direct evidence that Hepadnaviridae already existed during the Early Mesozoic. This implies that the Mesozoic fossil record of HBV infection spans three of the five major groups of land vertebrates, namely birds, crocodilians, and turtles. We show that the deep phylogenetic relationships of HBVs are largely congruent with the deep phylogeny of their amniote hosts, which suggests an ancient amniote–HBV coexistence and codivergence, at least since the Early Mesozoic. Notably, the organization of overlapping genes as well as the structure of elements involved in viral replication has remained highly conserved among HBVs along that time span, except for the presence of the X gene. We provide multiple lines of evidence that the tumor-promoting X protein of mammalian HBVs lacks a homolog in all other hepadnaviruses and propose a novel scenario for the emergence of X via segmental duplication and overprinting of pre-existing reading frames in the ancestor of mammalian HBVs. Our study reveals an unforeseen host range of prehistoric HBVs and provides novel insights into the genome evolution of hepadnaviruses throughout their long-lasting association with amniote hosts. PMID:25501991

  14. Coexistence of pheochromocytoma with uncommon vascular lesions

    PubMed Central

    Kota, Sunil Kumar; Kota, Siva Krishna; Meher, Lalit Kumar; Jammula, Sruti; Panda, Sandip; Modi, Kirtikumar D.

    2012-01-01

    Background: Pheochromocytoma/paragangliomas have been described to be associated with rare vascular abnormalities like renal artery stenosis. Coexistence of physiologically significant renal artery lesions is a compounding factor that alters management and prognosis of pheochromocytoma patients. Apart from individual case reports, data on such association in Indian population is not available. The aim of this study is to find the nature and prevalence of associated vascular abnormalities. Materials and Methods: From 1990 to 2010, a total of 50 patients were diagnosed with pheochromocytoma/paragangliomas. Hospital charts of these patients were reviewed retrospectively to identify those with unusual vascular abnormalities. Available literature was also reviewed. Results: Of the 50 patients with pheochromocytoma, 7 (14%) had coexisting vascular lesions including renal artery stenosis in 4, aortoarteritis in 1, aortic aneurysm in 1 and inferior vena cava thrombosis in 1. Pheochromocytoma was adrenal in 42 and extra adrenal in 8. Laparoscopic adrenalectomy was done in the patients. One patient with renal artery stenosis due to intimal fibrosis was subjected to percutaneous balloon angioplasty; the other three improved after adrenalectomy and lysis of fibrous adhesive bands. The patient with aortoarteritos was treated with oral steroids. Inferior vena cava thrombosis was reversed with anticoagulants. The patient with abdominal aortic aneurysm was advised for annual follow-up on account of its size of 4.5 cm and asymptomatic presentation. Conclusion: There are multiple mechanisms that can lead to renal artery stenosis and other vascular abnormalities in a case of pheochromocytoma. A high index of suspicion is necessary to enable both entities to be diagnosed preoperatively and allow proper planning of surgical therapy. Incomplete diagnosis may lead to persistent hypertension postoperatively in a case of associated renal artery stenosis. PMID:23226643

  15. Coexistence of pheochromocytoma with uncommon vascular lesions.

    PubMed

    Kota, Sunil Kumar; Kota, Siva Krishna; Meher, Lalit Kumar; Jammula, Sruti; Panda, Sandip; Modi, Kirtikumar D

    2012-11-01

    Pheochromocytoma/paragangliomas have been described to be associated with rare vascular abnormalities like renal artery stenosis. Coexistence of physiologically significant renal artery lesions is a compounding factor that alters management and prognosis of pheochromocytoma patients. Apart from individual case reports, data on such association in Indian population is not available. The aim of this study is to find the nature and prevalence of associated vascular abnormalities. From 1990 to 2010, a total of 50 patients were diagnosed with pheochromocytoma/paragangliomas. Hospital charts of these patients were reviewed retrospectively to identify those with unusual vascular abnormalities. Available literature was also reviewed. Of the 50 patients with pheochromocytoma, 7 (14%) had coexisting vascular lesions including renal artery stenosis in 4, aortoarteritis in 1, aortic aneurysm in 1 and inferior vena cava thrombosis in 1. Pheochromocytoma was adrenal in 42 and extra adrenal in 8. Laparoscopic adrenalectomy was done in the patients. One patient with renal artery stenosis due to intimal fibrosis was subjected to percutaneous balloon angioplasty; the other three improved after adrenalectomy and lysis of fibrous adhesive bands. The patient with aortoarteritos was treated with oral steroids. Inferior vena cava thrombosis was reversed with anticoagulants. The patient with abdominal aortic aneurysm was advised for annual follow-up on account of its size of 4.5 cm and asymptomatic presentation. There are multiple mechanisms that can lead to renal artery stenosis and other vascular abnormalities in a case of pheochromocytoma. A high index of suspicion is necessary to enable both entities to be diagnosed preoperatively and allow proper planning of surgical therapy. Incomplete diagnosis may lead to persistent hypertension postoperatively in a case of associated renal artery stenosis.

  16. Early mesozoic coexistence of amniotes and hepadnaviridae.

    PubMed

    Suh, Alexander; Weber, Claudia C; Kehlmaier, Christian; Braun, Edward L; Green, Richard E; Fritz, Uwe; Ray, David A; Ellegren, Hans

    2014-12-01

    Hepadnaviridae are double-stranded DNA viruses that infect some species of birds and mammals. This includes humans, where hepatitis B viruses (HBVs) are prevalent pathogens in considerable parts of the global population. Recently, endogenized sequences of HBVs (eHBVs) have been discovered in bird genomes where they constitute direct evidence for the coexistence of these viruses and their hosts from the late Mesozoic until present. Nevertheless, virtually nothing is known about the ancient host range of this virus family in other animals. Here we report the first eHBVs from crocodilian, snake, and turtle genomes, including a turtle eHBV that endogenized >207 million years ago. This genomic "fossil" is >125 million years older than the oldest avian eHBV and provides the first direct evidence that Hepadnaviridae already existed during the Early Mesozoic. This implies that the Mesozoic fossil record of HBV infection spans three of the five major groups of land vertebrates, namely birds, crocodilians, and turtles. We show that the deep phylogenetic relationships of HBVs are largely congruent with the deep phylogeny of their amniote hosts, which suggests an ancient amniote-HBV coexistence and codivergence, at least since the Early Mesozoic. Notably, the organization of overlapping genes as well as the structure of elements involved in viral replication has remained highly conserved among HBVs along that time span, except for the presence of the X gene. We provide multiple lines of evidence that the tumor-promoting X protein of mammalian HBVs lacks a homolog in all other hepadnaviruses and propose a novel scenario for the emergence of X via segmental duplication and overprinting of pre-existing reading frames in the ancestor of mammalian HBVs. Our study reveals an unforeseen host range of prehistoric HBVs and provides novel insights into the genome evolution of hepadnaviruses throughout their long-lasting association with amniote hosts.

  17. Three-Phase Coexistence in Lipid Membranes.

    PubMed

    Aufderhorst-Roberts, Anders; Chandra, Udayan; Connell, Simon D

    2017-01-24

    Phospholipid ternary systems are useful model systems for understanding lipid-lipid interactions and their influence on biological properties such as cell signaling and protein translocation. Despite extensive studies, there are still open questions relating to membrane phase behavior, particularly relating to a proposed state of three-phase coexistence, due to the difficulty in clearly distinguishing the three phases. We look in and around the region of the phase diagram where three phases are expected and use a combination of different atomic force microscopy (AFM) modes to present the first images of three coexisting lipid phases in biomimetic cell lipid membranes. Domains form through either nucleation or spinodal decomposition dependent upon composition, with some exhibiting both mechanisms in different domains simultaneously. Slow cooling rates are necessary to sufficiently separate mixtures with high proportions of lo and lβ phase. We probe domain heights and mechanical properties and demonstrate that the gel (lβ) domains have unusually low structural integrity in the three-phase region. This finding supports the hypothesis of a "disordered gel" state that has been proposed from NMR studies of similar systems, where the addition of small amounts of cholesterol was shown to disrupt the regular packing of the lβ state. We use NMR data from the literature on chain disorder in different mixtures and estimate an expected step height that is in excellent agreement with the AFM data. Alternatively, the disordered solid phase observed here and in the wider literature could be explained by the lβ phase being out of equilibrium, in a surface kinetically trapped state. This view is supported by the observation of unusual growth of nucleated domains, which we term "tree-ring growth," reflecting compositional heterogeneity in large disordered lβ phase domains.

  18. NUCLEAR REACTOR

    DOEpatents

    Grebe, J.J.

    1959-07-14

    High temperature reactors which are uniquely adapted to serve as the heat source for nuclear pcwered rockets are described. The reactor is comprised essentially of an outer tubular heat resistant casing which provides the main coolant passageway to and away from the reactor core within the casing and in which the working fluid is preferably hydrogen or helium gas which is permitted to vaporize from a liquid storage tank. The reactor core has a generally spherical shape formed entirely of an active material comprised of fissile material and a moderator material which serves as a diluent. The active material is fabricated as a gas permeable porous material and is interlaced in a random manner with very small inter-connecting bores or capillary tubes through which the coolant gas may flow. The entire reactor is divided into successive sections along the direction of the temperature gradient or coolant flow, each section utilizing materials of construction which are most advantageous from a nuclear standpoint and which at the same time can withstand the operating temperature of that particular zone. This design results in a nuclear reactor characterized simultaneously by a minimum critiral size and mass and by the ability to heat a working fluid to an extremely high temperature.

  19. The challenges of managing coexistent disorders with phenylketonuria: 30 cases.

    PubMed

    MacDonald, A; Ahring, K; Almeida, M F; Belanger-Quintana, A; Blau, N; Burlina, A; Cleary, M; Coskum, T; Dokoupil, K; Evans, S; Feillet, F; Giżewska, M; Gokmen Ozel, H; Lotz-Havla, A S; Kamieńska, E; Maillot, F; Lammardo, A M; Muntau, A C; Puchwein-Schwepcke, A; Robert, M; Rocha, J C; Santra, S; Skeath, R; Strączek, K; Trefz, F K; van Dam, E; van Rijn, M; van Spronsen, F; Vijay, S

    2015-12-01

    The few published case reports of co-existent disease with phenylketonuria (PKU) are mainly genetic and familial conditions from consanguineous marriages. The clinical and demographic features of 30 subjects with PKU and co-existent conditions were described in this multi-centre, retrospective cohort study. Diagnostic age of PKU and co-existent condition, treatment regimen, and impact of co-existent condition on blood phenylalanine (Phe) control and PKU management were reported. 30 patients (11 males and 19 females), with PKU and a co-existent condition, current median age of 14 years (range 0.4 to 40 years) from 13 treatment centres from Europe and Turkey were described. There were 21 co-existent conditions with PKU; 9 were autoimmune; 6 gastrointestinal, 3 chromosomal abnormalities, and 3 inherited conditions. There were only 5 cases of parental consanguinity. Some patients required conflicting diet therapy (n=5), nutritional support (n=7) and 5 children had feeding problems. There was delayed diagnosis of co-existent conditions (n=3); delayed treatment of PKU (n=1) and amenorrhea associated with Grave's disease that masked a PKU pregnancy for 12 weeks. Co-existent conditions adversely affected blood Phe control in 47% (n=14) of patients. Some co-existent conditions increased the complexity of disease management and increased management burden for patients and caregivers. Occurrence of co-existent disease is not uncommon in patients with PKU and so investigation for co-existent disorders when the clinical history is not completely consistent with PKU is essential. Integrating care of a second condition with PKU management is challenging. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Octocoral Species Assembly and Coexistence in Caribbean Coral Reefs

    PubMed Central

    Velásquez, Johanna; Sánchez, Juan A.

    2015-01-01

    Background What are the determinant factors of community assemblies in the most diverse ecosystem in the ocean? Coral reefs can be divided in continental (i.e., reefs that develop on the continental shelf, including siliciclastic reefs) and oceanic (i.e., far off the continental shelf, usually on volcanic substratum); whether or not these habitat differences impose community-wide ecological divergence or species exclusion/coexistence with evolutionary consequences, is unknown. Methods Studying Caribbean octocorals as model system, we determined the phylogenetic community structure in a coral reef community, making emphasis on species coexistence evidenced on trait evolution and environmental feedbacks. Forty-nine species represented in five families constituted the species pool from which a phylogenetic tree was reconstructed using mtDNA. We included data from 11 localities in the Western Caribbean (Colombia) including most reef types. To test diversity-environment and phenotype-environment relationships, phylogenetic community structure and trait evolution we carried out comparative analyses implementing ecological and evolutionary approaches. Results Phylogenetic inferences suggest clustering of oceanic reefs (e.g., atolls) contrasting with phylogenetic overdispersion of continental reefs (e.g., reefs banks). Additionally, atolls and barrier reefs had the highest species diversity (Shannon index) whereas phylogenetic diversity was higher in reef banks. The discriminant component analysis supported this differentiation between oceanic and continental reefs, where continental octocoral species tend to have greater calyx apertures, thicker branches, prominent calyces and azooxanthellate species. This analysis also indicated a clear separation between the slope and the remaining habitats, caused by the presence or absence of Symbiodinium. K statistic analysis showed that this trait is conserved as well as the branch shape. Discussion There was strong octocoral

  1. Octocoral Species Assembly and Coexistence in Caribbean Coral Reefs.

    PubMed

    Velásquez, Johanna; Sánchez, Juan A

    2015-01-01

    What are the determinant factors of community assemblies in the most diverse ecosystem in the ocean? Coral reefs can be divided in continental (i.e., reefs that develop on the continental shelf, including siliciclastic reefs) and oceanic (i.e., far off the continental shelf, usually on volcanic substratum); whether or not these habitat differences impose community-wide ecological divergence or species exclusion/coexistence with evolutionary consequences, is unknown. Studying Caribbean octocorals as model system, we determined the phylogenetic community structure in a coral reef community, making emphasis on species coexistence evidenced on trait evolution and environmental feedbacks. Forty-nine species represented in five families constituted the species pool from which a phylogenetic tree was reconstructed using mtDNA. We included data from 11 localities in the Western Caribbean (Colombia) including most reef types. To test diversity-environment and phenotype-environment relationships, phylogenetic community structure and trait evolution we carried out comparative analyses implementing ecological and evolutionary approaches. Phylogenetic inferences suggest clustering of oceanic reefs (e.g., atolls) contrasting with phylogenetic overdispersion of continental reefs (e.g., reefs banks). Additionally, atolls and barrier reefs had the highest species diversity (Shannon index) whereas phylogenetic diversity was higher in reef banks. The discriminant component analysis supported this differentiation between oceanic and continental reefs, where continental octocoral species tend to have greater calyx apertures, thicker branches, prominent calyces and azooxanthellate species. This analysis also indicated a clear separation between the slope and the remaining habitats, caused by the presence or absence of Symbiodinium. K statistic analysis showed that this trait is conserved as well as the branch shape. There was strong octocoral community structure with opposite diversity

  2. Coexisting Disorders and Academic Achievement among Children with ADHD

    ERIC Educational Resources Information Center

    Barnard-Brak, Lucy; Sulak, Tracey N.; Fearon, Danielle D.

    2011-01-01

    Objective: ADHD is a commonly diagnosed neuropsychological disorder among school-aged children with reported high rates of coexisting or comorbid disorders. As ADHD has been associated with academic underachievement, the current study examines this association in view of the presence of coexisting disorders. The purpose of the current study is to…

  3. Double Jeopardy for Children Who Stutter: Race and Coexisting Disorders

    ERIC Educational Resources Information Center

    Blood, Gordon W.; Blood, Ingrid; Kreiger, Jennifer; O'Connor, Shelah; Qualls, Constance Dean

    2009-01-01

    The primary purpose of this study was to examine the influence of racial and ethnic backgrounds in children who stutter (CWS) with 18 specific coexisting disorders. A sample of 1,184 speech-language pathologists responded to a detailed questionnaire designed to answer questions about the type and prevalence of coexisting disorders in 2,535 CWS.…

  4. Double Jeopardy for Children Who Stutter: Race and Coexisting Disorders

    ERIC Educational Resources Information Center

    Blood, Gordon W.; Blood, Ingrid; Kreiger, Jennifer; O'Connor, Shelah; Qualls, Constance Dean

    2009-01-01

    The primary purpose of this study was to examine the influence of racial and ethnic backgrounds in children who stutter (CWS) with 18 specific coexisting disorders. A sample of 1,184 speech-language pathologists responded to a detailed questionnaire designed to answer questions about the type and prevalence of coexisting disorders in 2,535 CWS.…

  5. 38 CFR 4.113 - Coexisting abdominal conditions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... SCHEDULE FOR RATING DISABILITIES Disability Ratings The Digestive System § 4.113 Coexisting abdominal conditions. There are diseases of the digestive system, particularly within the abdomen, which, while... coexisting diseases in this area, as indicated in the instruction under the title “Diseases of the Digestive...

  6. 38 CFR 4.113 - Coexisting abdominal conditions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... SCHEDULE FOR RATING DISABILITIES Disability Ratings The Digestive System § 4.113 Coexisting abdominal conditions. There are diseases of the digestive system, particularly within the abdomen, which, while... coexisting diseases in this area, as indicated in the instruction under the title “Diseases of the Digestive...

  7. 38 CFR 4.113 - Coexisting abdominal conditions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... SCHEDULE FOR RATING DISABILITIES Disability Ratings The Digestive System § 4.113 Coexisting abdominal conditions. There are diseases of the digestive system, particularly within the abdomen, which, while... coexisting diseases in this area, as indicated in the instruction under the title “Diseases of the Digestive...

  8. 38 CFR 4.113 - Coexisting abdominal conditions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... SCHEDULE FOR RATING DISABILITIES Disability Ratings The Digestive System § 4.113 Coexisting abdominal conditions. There are diseases of the digestive system, particularly within the abdomen, which, while... coexisting diseases in this area, as indicated in the instruction under the title “Diseases of the Digestive...

  9. 38 CFR 4.113 - Coexisting abdominal conditions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... SCHEDULE FOR RATING DISABILITIES Disability Ratings The Digestive System § 4.113 Coexisting abdominal conditions. There are diseases of the digestive system, particularly within the abdomen, which, while... coexisting diseases in this area, as indicated in the instruction under the title “Diseases of the Digestive...

  10. Coexistence of congenital linear porokeratosis and disseminated superficial porokeratosis.

    PubMed

    Cho, Eujin; Lee, Young Bok; Park, Hyun Jeong; Cho, Baik Kee

    2012-05-01

    The coexistence of two or more forms of porokeratosis in a single individual is rarely reported. We report here on a patient exhibiting the coexistence of congenital linear porokeratosis and disseminated superficial porokeratosis. To our knowledge, this entity has been previously reported only once. © 2011 The Authors. Australasian Journal of Dermatology © 2011 The Australasian College of Dermatologists.

  11. Glioma coexisting with angiographically occult cerebrovascular malformation: A case report

    PubMed Central

    Chen, Junhui; Chen, Lei; Zhang, Chunlei; He, Jianqing; Li, Peipei; Zhou, Jingxu; Zhu, Jun; Wang, Yuhai

    2016-01-01

    Angiographically occult cerebrovascular malformation (AOVM) is a type of complex cerebrovascular malformation that is not visible on digital subtraction angiography (DSA). Vascular malformation coexisting with glioma is clinically rare, and glioma coexisting with AOVM is even more rare. To the best of our knowledge, the present study is the first to report glioma coexisting with AOVM in the literature. The present study reports a rare case of glioma coexisting with AOVM in a 30-year-old male patient. Computed tomography (CT) scan revealed calcification, hemorrhage and edema in the right frontal lobe. CT angiography revealed a vascular malformation in the right frontal lobe, which was not observed on DSA. Finally, glioma coexisting with AOVM was confirmed by 2.0T magnetic resonance imaging and postoperative pathological examination. The present patient had a positive outcome and no neurological dysfunctions during the 6-month follow-up subsequent to surgery. PMID:27698825

  12. Exotic shapes and exotic clusterization

    SciTech Connect

    Cseh, J.; Darai, J.; Algora, A.

    2011-10-28

    The interrelation of the largely elongated nuclear shapes and clusterization is discussed by applying semimicroscopic methods. {sup 36}Ar is considered as a specific example, where recent experimental heavy-ion scattering data seem to justify the theoretical predictions on the hyperdeformed states. Alpha-emitting reactions are also suggested for its population.

  13. Coexistence of the α and δ phases in an as-cast uranium-rich U-Zr alloy

    NASA Astrophysics Data System (ADS)

    McKeown, J. T.; Irukuvarghula, S.; Ahn, S.; Wall, M. A.; Hsiung, L. L.; McDeavitt, S.; Turchi, P. E. A.

    2013-05-01

    Uranium-zirconium alloys are being investigated for use in ultrahigh burn-up, metallic inert matrix nuclear fuels. Characterization of these alloys in the transmission electron microscope with spatial resolutions that are inaccessible by other techniques shows that the orthorhombic α and hexagonal, intermetallic δ phases coexist in an as-cast uranium-rich U-10 wt.% Zr alloy. Analyses reveal the chemistries of and crystallographic relationship between the two phases.

  14. Coexistence of phage and bacteria on the boundary of self-organized refuges

    PubMed Central

    Heilmann, Silja; Sneppen, Kim; Krishna, Sandeep

    2012-01-01

    Bacteriophage are voracious predators of bacteria and a major determinant in shaping bacterial life strategies. Many phage species are virulent, meaning that infection leads to certain death of the host and immediate release of a large batch of phage progeny. Despite this apparent voraciousness, bacteria have stably coexisted with virulent phages for eons. Here, using individual-based stochastic spatial models, we study the conditions for achieving coexistence on the edge between two habitats, one of which is a bacterial refuge with conditions hostile to phage whereas the other is phage friendly. We show how bacterial density-dependent, or quorum-sensing, mechanisms such as the formation of biofilm can produce such refuges and edges in a self-organized manner. Coexistence on these edges exhibits the following properties, all of which are observed in real phage–bacteria ecosystems but difficult to achieve together in nonspatial ecosystem models: (i) highly efficient virulent phage with relatively long lifetimes, high infection rates and large burst sizes; (ii) large, stable, and high-density populations of phage and bacteria; (iii) a fast turnover of both phage and bacteria; and (iv) stability over evolutionary timescales despite imbalances in the rates of phage vs. bacterial evolution. PMID:22807479

  15. Aggression and coexistence in female caribou

    USGS Publications Warehouse

    Weckerly, Floyd W.; Ricca, Mark A.

    2014-01-01

    Female caribou (Rangifer tarandus) are highly gregarious, yet there has been little study of the behavioral mechanisms that foster coexistence. Quantifying patterns of aggression between male and female, particularly in the only cervid taxa where both sexes grow antlers, should provide insight into these mechanisms. We asked if patterns of aggression by male and female caribou followed the pattern typically noted in other polygynous cervids, in which males display higher frequencies and intensity of aggression. From June to August in 2011 and 2012, we measured the frequency and intensity of aggression across a range of group sizes through focal animal sampling of 170 caribou (64 males and 106 females) on Adak Island in the Aleutian Archipelago, Alaska. Males in same-sex and mixed-sex groups and females in mixed-sex groups had higher frequencies of aggression than females in same-sex groups. Group size did not influence frequency of aggression. Males displayed more intense aggression than females. Frequent aggression in mixed-sex groups probably reflects lower tolerance of males for animals in close proximity. Female caribou were less aggressive and more gregarious than males, as in other polygynous cervid species.

  16. Coexistent Sarcoidosis and Tuberculosis: A Case Report.

    PubMed

    Carbonelli, Cristiano; Giuffreda, Ernesto; Palmiotti, Antonio; Loizzi, Domenico; Lococo, Filippo; Carpagnano, Elisiana; Lacedonia, Donato; Sollitto, Francesco; Foschino, Maria Pia

    2017-02-09

    Necrotizing granulomatous diseases of the lungs are usually dependent on a narrow range of differential diagnoses. Tuberculosis (TB) is responsible for the largest number of cases, while necrotizing sarcoidosis is generally considered a rare and easily distinguishable disease substantially based on histological features. However, this entity has become a viable diagnosis in the absence of mycobacteria isolation or when a remarkable clinical improvement cannot be achieved with the combination of anti-TB drugs at full dosage. The classic manifestations of TB and sarcoidosis have an overlapping range for which it is sometimes difficult to make a clinical diagnosis. Furthermore, the role of mycobacteria as a trigger antigen capable of evoking the clinical expression of sarcoidosis is a hypothesis supported by evidence from some cases. We report a case of bilateral tuberculous pleurisy in a 45-year-old male native of a North-African region with an atypical severe multisystem disease characterized by a fever resistant to anti-TB therapy and respondent to corticosteroid treatment. The choice to continue both steroid and anti-TB therapy proved to be correct for the late evidence of TB mycobacterial growth only on pleural specimens. The case described is suggestive of a coexistent systemic sarcoid manifestation and low-antigen TB, which is an underrecognized entity in the medical literature.

  17. Coexistent anaphylaxis to Diptera and Hymenoptera.

    PubMed

    Freye, H B; Litwin, C

    1996-03-01

    Anaphylaxis to the bite of Diptera and specifically the bite of the Tabanidae family (horsefly) have been sparsely documented. The coexistent hypersensitivity to both the order Diptera and Hymenoptera has not been documented. We present a patient who experienced anaphylaxis to both insect species. Venom skin testing and RAST revealed sensitivity to several members of the Hymenoptera order. Prick, intradermal and RAST with whole body extracts of Tabanidae species is also documented in this patient. Twenty patients who are sensitive to Hymenoptera and have been bitten by horseflies but have had no reaction to the horsefly bite were used as controls. An anaphylactic reaction to horsefly bite has been documented in a 56-year-old white male. This patient also demonstrated evidence of anaphylactic reaction to Hymenoptera envenomation. In controls consisting of 20 patients with Hymenoptera sensitivity, there was no clinical history of reaction to horsefly bite despite the presence of positive prick and/or positive intradermal tests and/or positive RAST to mixed Tabanidae species extract. Skin testing to horsefly by prick and/or intradermal testing using whole body insect extract is not useful in making a diagnosis of Tabanidae hypersensitivity. RAST using Tabanidae species as antigen is similarly useless in making a diagnosis of Tabanidae hypersensitivity. In vivo and in vitro diagnosis of horsefly hypersensitivity may be achieved when the salivary gland antigen of the horsefly becomes available.

  18. A triplet of differently shaped spin-zero states in the atomic nucleus 186Pb

    PubMed

    Andreyev; Huyse; Van Duppen P; Weissman; Ackermann; Gerl; Hessberger; Hofmann; Kleinbohl; Munzenberg; Reshitko; Schlegel; Schaffner; Cagarda; Matos; Saro; Keenan; Moore; O'Leary; Page; Taylor; Kettunen; Leino; Lavrentiev; Wyss; Heyde

    2000-05-25

    Understanding the fundamental excitations of many-fermion systems is of significant current interest. In atomic nuclei with even numbers of neutrons and protons, the low-lying excitation spectrum is generally formed by nucleon pair breaking and nuclear vibrations or rotations. However, for certain numbers of protons and neutrons, a subtle rearrangement of only a few nucleons among the orbitals at the Fermi surface can result in a different elementary mode: a macroscopic shape change. The first experimental evidence for this phenomenon came from the observation of shape coexistence in 16O (ref. 4). Other unexpected examples came with the discovery of fission isomers and super-deformed nuclei. Here we find experimentally that the lowest three states in the energy spectrum of the neutron deficient nucleus 186Pb are spherical, oblate and prolate. The states are populated by the alpha-decay of a parent nucleus; to identify them, we combine knowledge of the particular features of this decay with sensitive measurement techniques (a highly efficient velocity filters with strong background reduction, and an extremely selective recoil-alpha-electron coincidence tagging methods). The existence of this apparently unique shape triplet is permitted only by the specific conditions that are met around this particular nucleus.

  19. Instance-Based Generative Biological Shape Modeling.

    PubMed

    Peng, Tao; Wang, Wei; Rohde, Gustavo K; Murphy, Robert F

    2009-01-01

    Biological shape modeling is an essential task that is required for systems biology efforts to simulate complex cell behaviors. Statistical learning methods have been used to build generative shape models based on reconstructive shape parameters extracted from microscope image collections. However, such parametric modeling approaches are usually limited to simple shapes and easily-modeled parameter distributions. Moreover, to maximize the reconstruction accuracy, significant effort is required to design models for specific datasets or patterns. We have therefore developed an instance-based approach to model biological shapes within a shape space built upon diffeomorphic measurement. We also designed a recursive interpolation algorithm to probabilistically synthesize new shape instances using the shape space model and the original instances. The method is quite generalizable and therefore can be applied to most nuclear, cell and protein object shapes, in both 2D and 3D.

  20. Nuclear Structure in China 2010

    NASA Astrophysics Data System (ADS)

    Bai, Hong-Bo; Meng, Jie; Zhao, En-Guang; Zhou, Shan-Gui

    2011-08-01

    Personal view on nuclear physics research / Jie Meng -- High-spin level structures in [symbol]Zr / X. P. Cao ... [et al.] -- Constraining the symmetry energy from the neutron skin thickness of tin isotopes / Lie-Wen Chen ... [et al.] -- Wobbling rotation in atomic nuclei / Y. S. Chen and Zao-Chun Gao -- The mixing of scalar mesons and the possible nonstrange dibaryons / L. R. Dai ... [et al.] -- Net baryon productions and gluon saturation in the SPS, RHIC and LHC energy regions / Sheng-Qin Feng -- Production of heavy isotopes with collisions between two actinide nuclides / Z. Q. Feng ... [et al.] -- The projected configuration interaction method / Zao-Chun Gao and Yong-Shou Chen -- Applications of Nilsson mean-field plus extended pairing model to rare-earth nuclei / Xin Guan ... [et al.] -- Complex scaling method and the resonant states / Jian-You Guo ... [et al.] -- Probing the equation of state by deep sub-barrier fusion reactions / Hong-Jun Hao and Jun-Long Tian -- Doublet structure study in A[symbol]105 mass region / C. Y. He ... [et al.] -- Rotational bands in transfermium nuclei / X. T. He -- Shape coexistence and shape evolution [symbol]Yb / H. Hua ... [et al.] -- Multistep shell model method in the complex energy plane / R. J. Liotta -- The evolution of protoneutron stars with kaon condensate / Ang Li -- High spin structures in the [symbol]Lu nucleus / Li Cong-Bo ... [et al.] -- Nuclear stopping and equation of state / QingFeng Li and Ying Yuan -- Covariant description of the low-lying states in neutron-deficient Kr isotopes / Z. X. Li ... [et al.] -- Isospin corrections for superallowed [symbol] transitions / HaoZhao Liang ... [et al.] -- The positive-parity band structures in [symbol]Ag / C. Liu ... [et al.] -- New band structures in odd-odd [symbol]I and [symbol]I / Liu GongYe ... [et al.] -- The sd-pair shell model and interacting boson model / Yan-An Luo ... [et al.] -- Cross-section distributions of fragments in the calcium isotopes projectile

  1. Long-Term Coexistence of Rotifer Cryptic Species

    PubMed Central

    Serra, Manuel; Gómez, Africa

    2011-01-01

    Despite their high morphological similarity, cryptic species often coexist in aquatic habitats presenting a challenge in the framework of niche differentiation theory and coexistence mechanisms. Here we use a rotifer species complex inhabiting highly unpredictable and fluctuating salt lakes to gain insights into the mechanisms involved in stable coexistence in cryptic species. We combined molecular barcoding surveys of planktonic populations and paleogenetic analysis of diapausing eggs to reconstruct the current and historical coexistence dynamics of two highly morphologically similar rotifer species, B. plicatilis and B. manjavacas. In addition, we carried out laboratory experiments using clones isolated from eight lakes where both species coexist to explore their clonal growth responses to salinity, a challenging, highly variable and unpredictable condition in Mediterranean salt lakes. We show that both species have co-occurred in a stable way in one lake, with population fluctuations in which no species was permanently excluded. The seasonal occurrence patterns of the plankton in two lakes agree with laboratory experiments showing that both species differ in their optimal salinity. These results suggest that stable species coexistence is mediated by differential responses to salinity and its fluctuating regime. We discuss the role of fluctuating salinity and a persistent diapausing egg banks as a mechanism for species coexistence in accordance with the ‘storage effect’. PMID:21738691

  2. Pollinator Foraging Adaptation and Coexistence of Competing Plants.

    PubMed

    Revilla, Tomás A; Křivan, Vlastimil

    2016-01-01

    We use the optimal foraging theory to study coexistence between two plant species and a generalist pollinator. We compare conditions for plant coexistence for non-adaptive vs. adaptive pollinators that adjust their foraging strategy to maximize fitness. When pollinators have fixed preferences, we show that plant coexistence typically requires both weak competition between plants for resources (e.g., space or nutrients) and pollinator preferences that are not too biased in favour of either plant. We also show how plant coexistence is promoted by indirect facilitation via the pollinator. When pollinators are adaptive foragers, pollinator's diet maximizes pollinator's fitness measured as the per capita population growth rate. Simulations show that this has two conflicting consequences for plant coexistence. On the one hand, when competition between pollinators is weak, adaptation favours pollinator specialization on the more profitable plant which increases asymmetries in plant competition and makes their coexistence less likely. On the other hand, when competition between pollinators is strong, adaptation promotes generalism, which facilitates plant coexistence. In addition, adaptive foraging allows pollinators to survive sudden loss of the preferred plant host, thus preventing further collapse of the entire community.

  3. Pollinator Foraging Adaptation and Coexistence of Competing Plants

    PubMed Central

    Revilla, Tomás A.; Křivan, Vlastimil

    2016-01-01

    We use the optimal foraging theory to study coexistence between two plant species and a generalist pollinator. We compare conditions for plant coexistence for non-adaptive vs. adaptive pollinators that adjust their foraging strategy to maximize fitness. When pollinators have fixed preferences, we show that plant coexistence typically requires both weak competition between plants for resources (e.g., space or nutrients) and pollinator preferences that are not too biased in favour of either plant. We also show how plant coexistence is promoted by indirect facilitation via the pollinator. When pollinators are adaptive foragers, pollinator’s diet maximizes pollinator’s fitness measured as the per capita population growth rate. Simulations show that this has two conflicting consequences for plant coexistence. On the one hand, when competition between pollinators is weak, adaptation favours pollinator specialization on the more profitable plant which increases asymmetries in plant competition and makes their coexistence less likely. On the other hand, when competition between pollinators is strong, adaptation promotes generalism, which facilitates plant coexistence. In addition, adaptive foraging allows pollinators to survive sudden loss of the preferred plant host, thus preventing further collapse of the entire community. PMID:27505254

  4. Nuclear power and nuclear weapons

    SciTech Connect

    Vaughen, V.C.A.

    1983-01-01

    The proliferation of nuclear weapons and the expanded use of nuclear energy for the production of electricity and other peaceful uses are compared. The difference in technologies associated with nuclear weapons and nuclear power plants are described.

  5. Coexistence of competitors mediated by nonlinear noise

    NASA Astrophysics Data System (ADS)

    Siekmann, Ivo; Bengfort, Michael; Malchow, Horst

    2017-06-01

    Stochastic reaction-diffusion equations are a popular modelling approach for studying interacting populations in a heterogeneous environment under the influence of environmental fluctuations. Although the theoretical basis of alternative models such as Fokker-Planck diffusion is not less convincing, movement of populations is most commonly modelled using the diffusion law due to Fick. An interesting feature of Fokker-Planck diffusion is the fact that for spatially varying diffusion coefficients the stationary solution is not a homogeneous distribution - in contrast to Fick's law of diffusion. Instead, concentration accumulates in regions of low diffusivity and tends to lower levels for areas of high diffusivity. Thus, we may interpret the stationary distribution of the Fokker-Planck diffusion as a reflection of different levels of habitat quality. Moreover, the most common model for environmental fluctuations, linear multiplicative noise, is based on the assumption that individuals respond independently to stochastic environmental fluctuations. For large population densities the assumption of independence is debatable and the model further implies that noise intensities can increase to arbitrarily high levels. Therefore, instead of the commonly used linear multiplicative noise model, we implement environmental variability by an alternative nonlinear noise term which never exceeds a certain maximum noise intensity. With Fokker-Planck diffusion and the nonlinear noise model replacing the classical approaches we investigate a simple invasive system based on the Lotka-Volterra competition model. We observe that the heterogeneous stationary distribution generated by Fokker-Planck diffusion generally facilitates the formation of segregated habitats of resident and invader. However, this segregation can be broken by nonlinear noise leading to coexistence of resident and invader across the whole spatial domain, an effect that would not be possible in the non

  6. Coexistence of fisheries with river dolphin conservation.

    PubMed

    Kelkar, Nachiket; Krishnaswamy, Jagdish; Choudhary, Sunil; Sutaria, Dipani

    2010-08-01

    Freshwater biodiversity conservation is generally perceived to conflict with human use and extraction (e.g., fisheries). Overexploited fisheries upset the balance between local economic needs and endangered species' conservation. We investigated resource competition between fisheries and Ganges river dolphins (Platanista gangetica gangetica) in a human-dominated river system in India to assess the potential for their coexistence. We surveyed a 65-km stretch of the lower Ganga River to assess habitat use by dolphins (encounter rates) and fishing activity (habitat preferences of fishers, intensity of net and boat use). Dolphin abundance in the main channel increased from 179 (SE 7) (mid dry season) to 270 (SE 8) (peak dry season), probably as a result of immigration from upstream tributaries. Dolphins preferred river channels with muddy, rocky substrates, and deep midchannel waters. These areas overlapped considerably with fishing areas. Sites with 2-6 boats/km (moderately fished) were more preferred by dolphins than sites with 8-55 boats/km (heavily fished). Estimated spatial (85%) and prey-resource overlap (75%) between fisheries and dolphins (chiefly predators of small fish) suggests a high level of competition between the two groups. A decrease in abundance of larger fish, indicated by the fact that small fish comprised 74% of the total caught, may have intensified the present competition. Dolphins seem resilient to changes in fish community structure and may persist in overfished rivers. Regulated fishing in dolphin hotspots and maintenance of adequate dry season flows can sustain dolphins in tributaries and reduce competition in the main river. Fish-stock restoration and management, effective monitoring, curbing destructive fishing practices, secure tenure rights, and provision of alternative livelihoods for fishers may help reconcile conservation and local needs in overexploited river systems.

  7. Diversity and becoming: implications of human existence as coexistence.

    PubMed

    Cody, William K

    2003-07-01

    Better ways of understanding and working with human diversity are needed in the healthcare and human service disciplines. Nursing, as the discipline that cares for whole persons throughout their lives and meets people where they are, is ideally suited to provide leadership to this effort. In this column, the author explores human diversity by explicating human existence as coexistence, with implications for nursing. The author locates his worldview within the human becoming school of thought. Human diversity and human existence as coexistence are explored within this context, with implications for nursing as a discipline identified. Ideas that are crucial in the explication of human existence as coexistence are difference, imagination, creativity, and wholeness.

  8. Nuclear rights - nuclear wrongs

    SciTech Connect

    Paul, E.F.; Miller, F.D.; Paul, J.; Ahrens, J.

    1986-01-01

    This book contains 11 selections. The titles are: Three Ways to Kill Innocent Bystanders: Some Conundrums Concerning the Morality of War; The International Defense of Liberty; Two Concepts of Deterrence; Nuclear Deterrence and Arms Control; Ethical Issues for the 1980s; The Moral Status of Nuclear Deterrent Threats; Optimal Deterrence; Morality and Paradoxical Deterrence; Immoral Risks: A Deontological Critique of Nuclear Deterrence; No War Without Dictatorship, No Peace Without Democracy: Foreign Policy as Domestic Politics; Marxism-Leninism and its Strategic Implications for the United States; Tocqueveille War.

  9. Nuclear physics: Macroscopic aspects

    SciTech Connect

    Swiatecki, W.J.

    1993-12-01

    A systematic macroscopic, leptodermous approach to nuclear statics and dynamics is described, based formally on the assumptions {h_bar} {yields} 0 and b/R << 1, where b is the surface diffuseness and R the nuclear radius. The resulting static model of shell-corrected nuclear binding energies and deformabilities is accurate to better than 1 part in a thousand and yields a firm determination of the principal properties of the nuclear fluid. As regards dynamics, the above approach suggests that nuclear shape evolutions will often be dominated by dissipation, but quantitative comparisons with experimental data are more difficult than in the case of statics. In its simplest liquid drop version the model exhibits interesting formal connections to the classic astronomical problem of rotating gravitating masses.

  10. Competition and coexistence with multiple life-history stages.

    PubMed

    Moll, Jason D; Brown, Joel S

    2008-06-01

    Do complex life histories affect the conditions under which competitors can coexist? We investigated this using a two-species, two-stage Ricker model. With complex life cycles, the competition coefficients associated with each life-history stage suggest one of three competitive outcomes-coexistence, alternate stable states, or competitive exclusion-that depend on the relative magnitudes of intraspecific and interspecific competition. When the two stages suggest the same outcome, only that outcome can occur. When the stages suggest different outcomes, either one may prevail. It is also possible to have emergent outcomes, in which the outcome is not suggested by either stage. This can occur when the two stages suggest competitive exclusion by opposite species or when one stage suggests alternate stable states and the other suggests coexistence. Therefore, determining the mechanisms of coexistence in species with complex life histories may require consideration of competitive interactions within all life-history stages.

  11. Opting out against defection leads to stable coexistence with cooperation

    PubMed Central

    Zhang, Bo-Yu; Fan, Song-Jia; Li, Cong; Zheng, Xiu-Deng; Bao, Jian-Zhang; Cressman, Ross; Tao, Yi

    2016-01-01

    Cooperation coexisting with defection is a common phenomenon in nature and human society. Previous studies for promoting cooperation based on kin selection, direct and indirect reciprocity, graph selection and group selection have provided conditions that cooperators outcompete defectors. However, a simple mechanism of the long-term stable coexistence of cooperation and defection is still lacking. To reveal the effect of direct reciprocity on the coexistence of cooperation and defection, we conducted a simple experiment based on the Prisoner’s Dilemma (PD) game, where the basic idea behind our experiment is that all players in a PD game should prefer a cooperator as an opponent. Our experimental and theoretical results show clearly that the strategies allowing opting out against defection are able to maintain this stable coexistence. PMID:27775099

  12. Opting out against defection leads to stable coexistence with cooperation.

    PubMed

    Zhang, Bo-Yu; Fan, Song-Jia; Li, Cong; Zheng, Xiu-Deng; Bao, Jian-Zhang; Cressman, Ross; Tao, Yi

    2016-10-24

    Cooperation coexisting with defection is a common phenomenon in nature and human society. Previous studies for promoting cooperation based on kin selection, direct and indirect reciprocity, graph selection and group selection have provided conditions that cooperators outcompete defectors. However, a simple mechanism of the long-term stable coexistence of cooperation and defection is still lacking. To reveal the effect of direct reciprocity on the coexistence of cooperation and defection, we conducted a simple experiment based on the Prisoner's Dilemma (PD) game, where the basic idea behind our experiment is that all players in a PD game should prefer a cooperator as an opponent. Our experimental and theoretical results show clearly that the strategies allowing opting out against defection are able to maintain this stable coexistence.

  13. Coexisting avascular necrosis of the scaphoid and lunate.

    PubMed

    Park, Il-Jung; Lee, Sang-Uk; Kim, Hyoung-Min

    2010-11-01

    Reports of coexisting avascular necrosis of more than one carpal bone are rare. We report coexisting avascular necrosis of the scaphoid and lunate in a 56-year-old woman with no history of using steroids or injury. We treated her with a radioscapholunate fusion with two angled 2.4 mm distal radius plates to stabilise the locking plate. At her 12-month follow up there was no evidence of non-union.

  14. Coexistence of pulmonary tuberculosis and sarcoidosis: a diagnostic dilemma.

    PubMed

    Mandal, Sanjay Kumar; Ghosh, Sudip; Mondal, Soumya Sarathi; Chatterjee, Sumanta

    2014-12-19

    Tuberculosis and sarcoidosis are multisystem diseases having different aetiology and management; however, they have similar clinical and histological characteristics. Very rarely they may coexist. We report a rare case of a 38-year-old woman who presented with chronic cough, low-grade fever and respiratory distress that was initially diagnosed as miliary tuberculosis. Diagnosis was supported by positive mycobacterial culture and initially responded to antitubercular treatment, but later recurrences led to further investigations and the diagnosis of coexisting sarcoidosis.

  15. Shape evolution of 72,74Kr with temperature in covariant density functional theory

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Niu, Yi-Fei

    2017-09-01

    The rich phenomena of deformations in neutron-deficient krypton isotopes, such as shape evolution with neutron number and shape coexistence, have attracted the interest of nuclear physicists for decades. It is interesting to study such shape phenomena using a novel way, e.g. by thermally exciting the nucleus. In this work, we develop the finite temperature covariant density functional theory for axially deformed nuclei with the treatment of pairing correlations by the BCS approach, and apply this approach for the study of shape evolution in 72,74Kr with increasing temperature. For 72Kr, with temperature increasing, the nucleus firstly experiences a relatively quick weakening in oblate deformation at temperature T ∼0.9 MeV, and then changes from oblate to spherical at T ∼2.1 MeV. For 74Kr, its global minimum is at quadrupole deformation β2 ∼ ‑0.14 and abruptly changes to spherical at T∼ 1.7 MeV. The proton pairing transition occurs at critical temperature 0.6 MeV following the rule Tc=0.6Δp(0), where Δp(0) is the proton pairing gap at zero temperature. The signatures of the above pairing transition and shape changes can be found in the specific heat curve. The single-particle level evolutions with temperature are presented. Supported by National Natural Science Foundation of China (11105042, 11305161, 11505157), Open Fund of Key Laboratory of Time and Frequency Primary Standards, CAS, and Support from Henan Administration of Foreign Experts Affairs

  16. Reexamining the nuclear structure of 154Gd in the dynamic pairing plus quadrupole model

    NASA Astrophysics Data System (ADS)

    Gupta, J. B.; Hamilton, J. H.

    2017-05-01

    In a previous study of the collective multiphonon bands in 154Gd, using the microscopic dynamic pairing plus quadrupole model, data for eight K bands were analyzed. In the last four decades, its decay scheme is significantly revised and the nuclear theory has undergone a significant change. Special focus is on new weak intensity transitions in several bands and on the reassigned levels in its decay scheme. The present study represents a detailed revised analysis of the collective even parity bands below 2.1 MeV. Also, a discussion is given on the nature of the Kπ=0+ excited bands, validity of band mixing approach, and of the assumption of shape coexistence of β band with ground band. Comparison is made with the X (5) analytical symmetry and the algebraic interacting boson model predictions. Discussion of the 2 n transfer reactions is given. The validity of the multiphonon view of the Kπ=4+ and 22+ bands is also studied.

  17. Nuclear structure of the N = 90 isotones

    NASA Astrophysics Data System (ADS)

    Kulp, William David, III

    2001-10-01

    Excited states in the transitional nucleus G15464d were studied through γ-ray spectroscopy following the β - decay of E15463u and the β+/EC decay of T154g,m1 ,m2 65b . The experimental data were obtained at the 88' Cyclotron at Lawrence Berkeley National Laboratory through radioactive sources placed in the 8π γ- ray Spectrometer (8π). Analysis of γ-ray singles spectra and γ-ray-gated γ-ray coincidence spectra resulted in the discovery of shape coexistence in 154Gd and the establishment of a level scheme for 154Gd which differs significantly from the adopted scheme. The primary motivation for this study was to examine the noticeable differences in structure above 1 MeV in the otherwise remarkably similar nuclei, 152Sm, 154Gd, and 156Dy. These nuclei lie at an abrupt transition between spherical and rotational nuclear shapes and, because of this, have been the subjects of intensive study. The use of the 8π marked the first time a large Compton-suppressed detector array has been used to study 154Gd, and the results presented in this work impact both the level scheme for 154Gd and the interpretation of the underlying structure of the nuclide. A new band mixing interpretation is presented which challenges the classic collective model interpretation of 154Gd. The model describes the low-lying structure of 154Gd through two configurations of different deformation which interact and mix to form the structure observed. The origin of the different deformations is attributed to a subshell closure at Z = 64.

  18. Intraspecific genetic variation and species coexistence in plant communities

    PubMed Central

    Ehlers, Bodil K.; Damgaard, Christian F.; Laroche, Fabien

    2016-01-01

    Many studies report that intraspecific genetic variation in plants can affect community composition and coexistence. However, less is known about which traits are responsible and the mechanisms by which variation in these traits affect the associated community. Focusing on plant–plant interactions, we review empirical studies exemplifying how intraspecific genetic variation in functional traits impacts plant coexistence. Intraspecific variation in chemical and architectural traits promotes species coexistence, by both increasing habitat heterogeneity and altering competitive hierarchies. Decomposing species interactions into interactions between genotypes shows that genotype × genotype interactions are often intransitive. The outcome of plant–plant interactions varies with local adaptation to the environment and with dominant neighbour genotypes, and some plants can recognize the genetic identity of neighbour plants if they have a common history of coexistence. Taken together, this reveals a very dynamic nature of coexistence. We outline how more traits mediating plant–plant interactions may be identified, and how future studies could use population genetic surveys of genotype distribution in nature and methods from trait-based ecology to better quantify the impact of intraspecific genetic variation on plant coexistence. PMID:26790707

  19. Tradeoffs, competition, and coexistence in eastern deciduous forest ant communities.

    PubMed

    Stuble, Katharine L; Rodriguez-Cabal, Mariano A; McCormick, Gail L; Jurić, Ivan; Dunn, Robert R; Sanders, Nathan J

    2013-04-01

    Ecologists have long sought to explain the coexistence of multiple potentially competing species in local assemblages. This is especially challenging in species-rich assemblages in which interspecific competition is intense, as it often is in ant assemblages. As a result, a suite of mechanisms has been proposed to explain coexistence among potentially competing ant species: the dominance-discovery tradeoff, the dominance-thermal tolerance tradeoff, spatial segregation, temperature-based niche partitioning, and temporal niche partitioning. Through a series of observations and experiments, we examined a deciduous forest ant assemblage in eastern North America for the signature of each of these coexistence mechanisms. We failed to detect evidence for any of the commonly suggested mechanisms of coexistence, with one notable exception: ant species appear to temporally partition foraging times such that behaviourally dominant species foraged more intensely at night, while foraging by subdominant species peaked during the day. Our work, though focused on a single assemblage, indicates that many of the commonly cited mechanisms of coexistence may not be general to all ant assemblages. However, temporal segregation may play a role in promoting coexistence among ant species in at least some ecosystems, as it does in many other organisms.

  20. Intraspecific genetic variation and species coexistence in plant communities.

    PubMed

    Ehlers, Bodil K; Damgaard, Christian F; Laroche, Fabien

    2016-01-01

    Many studies report that intraspecific genetic variation in plants can affect community composition and coexistence. However, less is known about which traits are responsible and the mechanisms by which variation in these traits affect the associated community. Focusing on plant-plant interactions, we review empirical studies exemplifying how intraspecific genetic variation in functional traits impacts plant coexistence. Intraspecific variation in chemical and architectural traits promotes species coexistence, by both increasing habitat heterogeneity and altering competitive hierarchies. Decomposing species interactions into interactions between genotypes shows that genotype × genotype interactions are often intransitive. The outcome of plant-plant interactions varies with local adaptation to the environment and with dominant neighbour genotypes, and some plants can recognize the genetic identity of neighbour plants if they have a common history of coexistence. Taken together, this reveals a very dynamic nature of coexistence. We outline how more traits mediating plant-plant interactions may be identified, and how future studies could use population genetic surveys of genotype distribution in nature and methods from trait-based ecology to better quantify the impact of intraspecific genetic variation on plant coexistence. © 2016 The Author(s).

  1. Persistent coexistence of cyclically competing species in spatially extended ecosystems

    NASA Astrophysics Data System (ADS)

    Park, Junpyo; Do, Younghae; Huang, Zi-Gang; Lai, Ying-Cheng

    2013-06-01

    A fundamental result in the evolutionary-game paradigm of cyclic competition in spatially extended ecological systems, as represented by the classic Reichenbach-Mobilia-Frey (RMF) model, is that high mobility tends to hamper or even exclude species coexistence. This result was obtained under the hypothesis that individuals move randomly without taking into account the suitability of their local environment. We incorporate local habitat suitability into the RMF model and investigate its effect on coexistence. In particular, we hypothesize the use of "basic instinct" of an individual to determine its movement at any time step. That is, an individual is more likely to move when the local habitat becomes hostile and is no longer favorable for survival and growth. We show that, when such local habitat suitability is taken into account, robust coexistence can emerge even in the high-mobility regime where extinction is certain in the RMF model. A surprising finding is that coexistence is accompanied by the occurrence of substantial empty space in the system. Reexamination of the RMF model confirms the necessity and the important role of empty space in coexistence. Our study implies that adaptation/movements according to local habitat suitability are a fundamental factor to promote species coexistence and, consequently, biodiversity.

  2. The nuclear DNA longevity in cryopreserved boar spermatozoa assessed using the Sperm-Sus-Halomax.

    PubMed

    Alkmin, Diego V; Martinez-Alborcia, Maria J; Parrilla, Inmaculada; Vazquez, Juan M; Martinez, Emilio A; Roca, Jordi

    2013-06-01

    The aim of this experimental study was to evaluate the dynamics of nuclear DNA fragmentation in frozen-thawed (FT) boar spermatozoa incubated over time. Using the Sperm Chromatin Dispersion test (Sperm-Sus-Halomax), this study focused special attention on resolving the hypothesis that the original halo shapes around the sperm head could show dynamic changes over the postthawing incubation time. Twenty FT sperm samples from five boars (four per boar) were incubated at 37 °C during 168 hours and sperm motility (assessed using computer-assisted sperm analysis), viability (evaluated using the LIVE/DEAD Sperm Viability Kit), and nuclear DNA fragmentation were analyzed at 0, 0.5, 2, 4, 6, 24, 48, 72, and 168 hours. The percentages of motile and viable spermatozoa progressively decreased during incubation, with no motile and viable spermatozoa less than 10% in all boars at 24 hours of incubation. Four different halo shapes around the sperm head were considered in the Sperm Chromatin Dispersion test: normal, small, large scattered (typical fragmented nuclear DNA), and absent halo, all of them coexisting at the same time in the boar FT semen samples. Sperm with a large scattered halo did not change during postthaw, consistently showing percentages less than 5% over time in all boars. In contrast, the other three sperm populations showed a dynamic evolution over incubation time, characterized by a gradual reduction of sperm with normal halo, proportional to the increment in the sperm showing a small halo, followed by a switch between the sperm with a small halo and sperm with no halo. These results suggest that three of these four sperm populations, those showing small, large scattered, and absent halo, represent spermatozoa with different degrees of nuclear DNA damage, which should be taken into consideration to indicate the percentage of sperm with fragmented nuclear DNA in boar FT semen samples.

  3. Decay-out of 151Tb Yrast Superdeformed Band and Shape Coexistence

    SciTech Connect

    Duchene, G.; Robin, J.; Odahara, A.; Byrski, Th.; Beck, F.A.; Bednarczyk, P.; Curien, D.; Courtin, S.; Dorvaux, O.; Gall, B.; Joshi, P.; Nourreddine, A.; Pachoud, E.; Piqueras, I.; Vivien, J.P.; Twin, P.J.; Cullen, D.M.; Ertueck, S.; King, S.L.; Paul, E.S.

    2004-02-27

    Linking transitions between the superdeformed (SD) and the normal deformed (ND) wells have been searched in 151Tb nucleus. Two experiments of 5 and 17 days have been performed with EUROBALL IV. Transitions of 2818 keV and 3748 keV with intensities of about 1 % relative to the yrast SD band have been observed. Their decay-out properties are discussed in the text. In addition the eight known SD bands have been extended towards higher rotational frequencies where orbital crossings are observed. For the first time, weakly populated collective ND structures, likely triaxial, similar to the ones recently identified in 152Dy, 153Ho and 155Er nuclei have been observed in 151Tb. The SD and ND structures are interpreted in the frame of Woods-Saxon theoretical calculations.

  4. 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.

  5. Decay-out of 151Tb Yrast Superdeformed Band and Shape Coexistence

    NASA Astrophysics Data System (ADS)

    Duchêne, G.; Robin, J.; Odahara, A.; Byrski, Th.; Beck, F. A.; Twin, P. J.; Bednarczyk, P.; Curien, D.; Courtin, S.; Dorvaux, O.; Gall, B.; Joshi, P.; Nourreddine, A.; Pachoud, E.; Piqueras, I.; Vivien, J. P.; Zuber, K.; Adimi, N.; Appelbe, D. E.; Bracco, A.; Cederwall, B.; Cullen, D. M.; Ertück, S.; de France, G.; King, S. L.; Korichi, A.; Lagergren, K.; Leoni, S.; Lo Bianco, G.; Lopez-Martens, A.; Lunardi, S.; Million, B.; Paul, E. S.; Petrache, C.; Redon, N.; Saltarelli, A.; Simpson, J.; Stézowski, O.; Venturelli, R.

    2004-02-01

    Linking transitions between the superdeformed (SD) and the normal deformed (ND) wells have been searched in 151Tb nucleus. Two experiments of 5 and 17 days have been performed with EUROBALL IV. Transitions of 2818 keV and 3748 keV with intensities of about 1 % relative to the yrast SD band have been observed. Their decay-out properties are discussed in the text. In addition the eight known SD bands have been extended towards higher rotational frequencies where orbital crossings are observed. For the first time, weakly populated collective ND structures, likely triaxial, similar to the ones recently identified in 152Dy, 153Ho and 155Er nuclei have been observed in 151Tb. The SD and ND structures are interpreted in the frame of Woods-Saxon theoretical calculations.

  6. Evidence for coexisting prolate and near-oblate shapes at high spin in 125Cs

    NASA Astrophysics Data System (ADS)

    Sun, Ji; Komatsubara, Tetsuro; Wang, Jia-Qi; Guo, Hao; Hu, Xue-Yuan; Ma, Ying-Jun; Liu, Yun-Zuo; Furuno, Kohei

    2016-12-01

    Excited states in the odd-proton nucleus 125Cs were investigated by means of in-beam γ -ray spectroscopy. The πg7/2 band is observed to fork into a ΔI = 1 coupled band and a ΔI = 2 decoupled band at high spins. To assign the possible configurations of these two bands, experimental B(M1)/B(E2) ratios and signature splittings have been evaluated for the ΔI = 1 band, and calculations based on the geometrical model, cranked shell model and total Routhian surfaces model have been performed. They are suggested to be a near-oblate band built on the (πg7/2/d5/2) ⊗ (νh11/2)2 configuration and a prolate band built on the πg7/2 ⊗ (πh11/2)2 configuration, respectively. Supported in part by National Natural Science Foundation of China (11475072)

  7. Deformation and mixing of coexisting shapes in neutron-deficient polonium isotopes

    NASA Astrophysics Data System (ADS)

    Kesteloot, N.; Bastin, B.; Gaffney, L. P.; Wrzosek-Lipska, K.; Auranen, K.; Bauer, C.; Bender, M.; Bildstein, V.; Blazhev, A.; Bönig, S.; Bree, N.; Clément, E.; Cocolios, T. E.; Damyanova, A.; Darby, I.; De Witte, H.; Di Julio, D.; Diriken, J.; Fransen, C.; García-Ramos, J. E.; Gernhäuser, R.; Grahn, T.; Heenen, P.-H.; Hess, H.; Heyde, K.; Huyse, M.; Iwanicki, J.; Jakobsson, U.; Konki, J.; Kröll, T.; Laurent, B.; Lecesne, N.; Lutter, R.; Pakarinen, J.; Peura, P.; Piselli, E.; Próchniak, L.; Rahkila, P.; Rapisarda, E.; Reiter, P.; Scheck, M.; Seidlitz, M.; Sferrazza, M.; Siebeck, B.; Sjodin, M.; Tornqvist, H.; Traykov, E.; Van De Walle, J.; Van Duppen, P.; Vermeulen, M.; Voulot, D.; Warr, N.; Wenander, F.; Wimmer, K.; Zielińska, M.

    2015-11-01

    Coulomb-excitation experiments are performed with postaccelerated beams of neutron-deficient Po 196 ,198 ,200 ,202 isotopes at the REX-ISOLDE facility. A set of matrix elements, coupling the low-lying states in these isotopes, is extracted. In the two heaviest isotopes, Po,202200, the transitional and diagonal matrix elements of the 21+ state are determined. In Po,198196 multistep Coulomb excitation is observed, populating the 41+,02+ , and 22+ states. The experimental results are compared to the results from the measurement of mean-square charge radii in polonium isotopes, confirming the onset of deformation from 196Po onwards. Three model descriptions are used to compare to the data. Calculations with the beyond-mean-field model, the interacting boson model, and the general Bohr Hamiltonian model show partial agreement with the experimental data. Finally, calculations with a phenomenological two-level mixing model hint at the mixing of a spherical structure with a weakly deformed rotational structure.

  8. Equilibrium Shaping

    NASA Astrophysics Data System (ADS)

    Izzo, Dario; Petazzi, Lorenzo

    2006-08-01

    We present a satellite path planning technique able to make identical spacecraft aquire a given configuration. The technique exploits a behaviour-based approach to achieve an autonomous and distributed control over the relative geometry making use of limited sensorial information. A desired velocity is defined for each satellite as a sum of different contributions coming from generic high level behaviours: forcing the final desired configuration the behaviours are further defined by an inverse dynamic calculation dubbed Equilibrium Shaping. We show how considering only three different kind of behaviours it is possible to acquire a number of interesting formations and we set down the theoretical framework to find the entire set. We find that allowing a limited amount of communication the technique may be used also to form complex lattice structures. Several control feedbacks able to track the desired velocities are introduced and discussed. Our results suggest that sliding mode control is particularly appropriate in connection with the developed technique.

  9. Nuclear Medicine.

    ERIC Educational Resources Information Center

    Badawi, Ramsey D.

    2001-01-01

    Describes the use of nuclear medicine techniques in diagnosis and therapy. Describes instrumentation in diagnostic nuclear medicine and predicts future trends in nuclear medicine imaging technology. (Author/MM)

  10. Nuclear ventriculography

    MedlinePlus

    ... ventriculography (RNV); Multiple gate acquisition scan (MUGA); Nuclear cardiology; Cardiomyopathy - nuclear ventriculography ... 56. Udelson JE, Dilsizian V, Bonow RO. Nuclear cardiology. In: Bonow RO, Mann DL, Zipes DP, Libby ...

  11. Nuclear Medicine.

    ERIC Educational Resources Information Center

    Badawi, Ramsey D.

    2001-01-01

    Describes the use of nuclear medicine techniques in diagnosis and therapy. Describes instrumentation in diagnostic nuclear medicine and predicts future trends in nuclear medicine imaging technology. (Author/MM)

  12. Nuclear data for nuclear transmutation

    SciTech Connect

    Harada, Hideo

    2009-05-04

    Current status on nuclear data for the study of nuclear transmutation of radioactive wastes is reviewed, mainly focusing on neutron capture reactions. It is stressed that the highest-precision frontier research in nuclear data measurements should be a key to satisfy the target accuracies on the nuclear data requested for realizing the nuclear transmutation.

  13. Nuclear data for nuclear transmutation

    NASA Astrophysics Data System (ADS)

    Harada, Hideo

    2009-05-01

    Current status on nuclear data for the study of nuclear transmutation of radioactive wastes is reviewed, mainly focusing on neutron capture reactions. It is stressed that the highest-precision frontier research in nuclear data measurements should be a key to satisfy the target accuracies on the nuclear data requested for realizing the nuclear transmutation.

  14. Two-dimensional shape memory graphene oxide

    PubMed Central

    Chang, Zhenyue; Deng, Junkai; Chandrakumara, Ganaka G.; Yan, Wenyi; Liu, Jefferson Zhe

    2016-01-01

    Driven by the increasing demand for micro-/nano-technologies, stimuli-responsive shape memory materials at nanoscale have recently attracted great research interests. However, by reducing the size of conventional shape memory materials down to approximately nanometre range, the shape memory effect diminishes. Here, using density functional theory calculations, we report the discovery of a shape memory effect in a two-dimensional atomically thin graphene oxide crystal with ordered epoxy groups, namely C8O. A maximum recoverable strain of 14.5% is achieved as a result of reversible phase transition between two intrinsically stable phases. Our calculations conclude co-existence of the two stable phases in a coherent crystal lattice, giving rise to the possibility of constructing multiple temporary shapes in a single material, thus, enabling highly desirable programmability. With an atomic thickness, excellent shape memory mechanical properties and electric field stimulus, the discovery of a two-dimensional shape memory graphene oxide opens a path for the development of exceptional micro-/nano-electromechanical devices. PMID:27325441

  15. Coexistence of competing metabolic pathways in well-mixed populations

    NASA Astrophysics Data System (ADS)

    Fernández, Lenin; Amado, André; Campos, Paulo R. A.; Ferreira, Fernando Fagundes

    2016-05-01

    Understanding why strains with different metabolic pathways that compete for a single limiting resource coexist is a challenging issue within a theoretical perspective. Previous investigations rely on mechanisms such as group or spatial structuring to achieve a stable coexistence between competing metabolic strategies. Nevertheless, coexistence has been experimentally reported even in situations where it cannot be attributed to spatial effects [Heredity 100, 471 (2008), 10.1038/sj.hdy.6801073]. According to that study a toxin expelled by one of the strains can be responsible for the stable maintenance of the two strain types. We propose a resource-based model in which an efficient strain with a slow metabolic rate competes with a second strain type which presents a fast but inefficient metabolism. Moreover, the model assumes that the inefficient strain produces a toxin as a by-product. This toxin affects the growth rate of both strains with different strength. Through an extensive exploration of the parameter space we determine the situations at which the coexistence of the two strains is possible. Interestingly, we observe that the resource influx rate plays a key role in the maintenance of the two strain types. In a scenario of resource scarcity the inefficient is favored, though as the resource influx rate is augmented the coexistence becomes possible and its domain is enlarged.

  16. Technocrats and nuclear politics

    SciTech Connect

    Massey, A.

    1988-01-01

    This book arrives in an age of growing unease and dissatisfaction with the reassurances, by the nuclear power industry, of the safety of its power stations. The book's central purpose is to examine the motivations and varied perceptions which have laid the foundation for Britain's contemporary civil nuclear industry. The author pays particular attention to the role and influence of technical experts in the shaping of decisions within their own industry and the implementation of those decisions at the government level. The author shows how, in the British model, ministers and civil servants tend to serve as policy arbiters who set the parameters within which the dynamics of special interest groups provide policy options. This book combines several current themes; the politics of nuclear energy; the role of professional experts; and the impact of and drive for privitization. It examines the process of modern British policy-making and nuclear power politics, and holds implications that reach far beyond Britain.

  17. Ground-state nuclear-moment measurement of neutron-rich sulfur isotopes

    NASA Astrophysics Data System (ADS)

    Ohtomo, Yuichi; Ichikawa, Yuichi; Shirai, Hazuki; Ueno, Hideki; Ishibashi, Youko; Suzuki, Takahiro; Furukawa, Takeshi; Yoshimi, Akihiro; Abe, Yasushi; Asahi, Koichiro; Daugasu, J. M.; Fujita, Tomomi; Hayasaka, Miki; Imamura, Kei; Kishi, Shota; Kojima, Shuichiro; Nagae, Daisuke; Nakao, Aiko; Sagayama, Tsubasa; Sakamoto, Yu; Sato, Tomoya

    2014-09-01

    Recently the erosion of N = 28 shell gap has been suggested from several spectroscopic experimental data on neutron-rich nuclei. In particular, 43S isotope is of much interest since shape coexistence is expected to occur which provides key information to understand the evolution of shell gaps far from the stability. The isomeric state of 43S at 320 keV is suggested to have a shape close to sphericity with spin-parity of 7/2, but both the spin-parity and deformed parameter of the ground-state have not been determined directly. In order to investigate mechanisms leading to such an anomalous nuclear structure, we aim at measuring the ground-state nuclear-moment for 41,43S. As the first step, the measurement of μ moment of 41S was performed using the technique of β-NMR method at the RIPS facility at RIKEN. In the presentation, the result of this work will be reported.

  18. Biodefense research: can secrecy and safety coexist?

    PubMed

    Kahn, Laura H

    2004-01-01

    Over the next 10 years, the United States will spend 6 billion US dollars to develop countermeasures against biological and chemical weapons. Much of this research on highly virulent pathogens will be done in academic settings around the country. This article explores the challenges in ensuring secrecy to protect national security while accommodating the right of local communities to have access to safety information regarding select agents and laboratory-acquired infections. Secrecy has been defended as being vital for protecting national security. Problems with secrecy can include the misinterpretation of intentions, particularly in laboratories located in nuclear weapons design facilities, and the restricted access to information relevant to public health and safety. While federal select agent legislation requires laboratories to have emergency plans in place with first responders, these plans do not necessarily include public health professionals, who will be responsible for any future public health action, such as quarantine, surveillance, or mass vaccinations, in the unlikely event that a laboratory-acquired infection spreads into a community. Laboratory-acquired infections do occur, even with the best safety mechanisms in place; however, the epidemiology of the incidence and severity of these infections are not known since there is no national surveillance reporting system. Evidence suggests that many of these infections occur in the absence of an actual laboratory accident. The best emergency plans and surveillance systems are only as good as the participation and vigilance of the laboratory workers themselves. Thus, laboratory workers have a responsibility to themselves and others to report all laboratory accidents and spills, regardless how minor. In addition, they should have a lower threshold than normal in seeking medical attention when feeling ill, and their physicians should be aware of what pathogens they work with to reduce the risk of a delay in

  19. Nuclear "waffles"

    NASA Astrophysics Data System (ADS)

    Schneider, A. S.; Berry, D. K.; Briggs, C. M.; Caplan, M. E.; Horowitz, C. J.

    2014-11-01

    Background: The dense neutron-rich matter found in supernovae and inside neutron stars is expected to form complex nonuniform phases, often referred to as nuclear pasta. The pasta shapes depend on density, temperature and proton fraction and determine many transport properties in supernovae and neutron star crusts. Purpose: To characterize the topology and compute two observables, the radial distribution function (RDF) g (r ) and the structure factor S (q ) , for systems with proton fractions Yp=0.10 ,0.20 ,0.30 , and 0.40 at about one-third of nuclear saturation density, n =0.050 fm-3 , and temperatures near k T =1 MeV . Methods: We use two recently developed hybrid CPU/GPU codes to perform large scale molecular dynamics (MD) simulations with 51 200 and 409 600 nucleons. From the output of the MD simulations we obtain the two desired observables. Results: We compute and discuss the differences in topology and observables for each simulation. We observe that the two lowest proton fraction systems simulated, Yp=0.10 and 0.20 , equilibrate quickly and form liquidlike structures. Meanwhile, the two higher proton fraction systems, Yp=0.30 and 0.40 , take a longer time to equilibrate and organize themselves in solidlike periodic structures. Furthermore, the Yp=0.40 system is made up of slabs, lasagna phase, interconnected by defects while the Yp=0.30 systems consist of a stack of perforated plates, the nuclear waffle phase. Conclusions: The periodic configurations observed in our MD simulations for proton fractions Yp≥0.30 have important consequences for the structure factors S (q ) of protons and neutrons, which relate to many transport properties of supernovae and neutron star crust. A detailed study of the waffle phase and how its structure depends on temperature, size of the simulation, and the screening length showed that finite-size effects appear to be under control and, also, that the plates in the waffle phase merge at temperatures slightly above 1.0 MeV and

  20. Dissipative curvature fluctuations in bilayer vesicles: Coexistence of pure-bending and hybrid curvature-compression modes.

    PubMed

    Arriaga, L R; Rodríguez-García, R; López-Montero, I; Farago, B; Hellweg, T; Monroy, F

    2010-01-01

    We have studied the relaxation dynamics of shape fluctuations in unilamellar lipid vesicles by neutron spin echo (NSE). The presence of a hybrid curvature-compression mode coexisting with the usual bending one has been revealed in the experimental relaxation functions at high q . Differently to the conventional relaxation approximately q (3) typical for bending modes, the hybrid mode was found to relax as approximately q (2) , which is compatible with a dissipation mechanism arising from intermonolayer friction. Complementary data obtained from flickering spectroscopy (FS) in giant unilamellar vesicles confirm the existence of both modes coexisting together. By combining NSE and FS data we have depicted the experimental bimodal dispersion diagram, which is found compatible with theoretical predictions for reliable values of the material parameters. From the present data two conventional dynamical methods (NSE and FS) have been shown to be suitable for measuring intermonolayer friction coefficients in bilayer vesicles.

  1. Sulfur hexafluoride's liquid-vapor coexistence curve, interfacial properties, and diffusion coefficients as predicted by a simple rigid model.

    PubMed

    Olivet, Aurelio; Duque, Daniel; Vega, Lourdes F

    2005-11-15

    We present here molecular-dynamics simulation results of the vapor-liquid coexistence curve, surface tension, and self-diffusion coefficients of sulfur hexafluoride. Sulfur hexafluoride is modeled as a rigid molecule, following the model proposed by Pawley [Mol. Phys. 43, 1321 (1981)]. Vapor-liquid coexistence curve and surface tension are obtained through direct molecular-dynamic simulations in the NVT ensemble. Simulation results are able to reproduce the qualitative shape of the vapor-liquid envelope. However, lower densities, a higher critical temperature, and an overestimated surface tension are obtained here. Those deviations are explained on the basis of the rigidity of the molecular model used. Self-diffusion coefficients are calculated from simulations in the NVE ensemble for different gas states at atmospheric pressure. The rigid model performs better for dynamical properties since simulation results provide very good agreement with available experimental data in this case.

  2. Superordinate Shape Classification Using Natural Shape Statistics

    ERIC Educational Resources Information Center

    Wilder, John; Feldman, Jacob; Singh, Manish

    2011-01-01

    This paper investigates the classification of shapes into broad natural categories such as "animal" or "leaf". We asked whether such coarse classifications can be achieved by a simple statistical classification of the shape skeleton. We surveyed databases of natural shapes, extracting shape skeletons and tabulating their…

  3. Superordinate Shape Classification Using Natural Shape Statistics

    ERIC Educational Resources Information Center

    Wilder, John; Feldman, Jacob; Singh, Manish

    2011-01-01

    This paper investigates the classification of shapes into broad natural categories such as "animal" or "leaf". We asked whether such coarse classifications can be achieved by a simple statistical classification of the shape skeleton. We surveyed databases of natural shapes, extracting shape skeletons and tabulating their…

  4. Influence of polymer molecular weight and concentration on coexistence curve of isobutyric acid + water.

    PubMed

    Reddy, P Madhusudhana; Venkatesu, P; Bohidar, H B

    2011-10-27

    We report the influence of variation of molecular weights (MWs = 2, 4, 6, and 9 × 10(5) g mol(-1)) and concentration (C) of a long-chain polymer (polyethylene oxide, PEO) on an upper critical solution temperature (UCST) of isobutyric acid (I) + water (W) using density (ρ) measurements as a function of temperature. The ρ values in each coexisting phase of IW have been measured at three different PEO concentrations (C = 0.395, 0.796, and 1.605 mg/cm(3)) in the near critical composition of IW at temperatures below the system's upper critical point for each molecular weight (MW) of PEO. Further, to ascertain the PEO behavior in IW we have measured the polydispersity values for both coexisting liquid phases by using dynamic light scattering (DLS). The data show that the polymer was significantly affected in the critical region of IW and these various MWs and concentrations of PEO show significant modulation on the critical exponents (β), the critical temperatures (T(c)), and critical composition (ϕ(c)), which are depicting the shape of the coexistence curve. The values of β and T(c) increase with increasing PEO MW and concentrations. Besides, the ϕ(c) values slightly decrease with increasing the C values in the mixture of IW. However, the rate of decrease in ϕ(c) is insignificant. Our experimental results explicitly elucidate that most of polymer chain entangles in water rich phase, thereby the polymer monomers strongly interact with neighbor solvent particles and also intra chain interaction between polymer monomers.

  5. The Coexistence of Rathke Cleft Cyst and Pituitary Adenoma.

    PubMed

    Gao, Mingtong; An, Yanyan; Huang, Zhihong; Niu, Jianyi; Yuan, Xunhui; Bai, Yun'an; Guo, Liemei

    2016-03-01

    Both of Pituitary adenoma (PA) and Rathke cleft cyst (RCC) are the most common and benign sellar lesions. Generally, the origin of RCC is considered to be derived from remnants of Rathke punch, while PA is formed by proliferation of the anterior wall of Rathke pouch. Although they have a possibility to share a common embryological origin, the coexistence of PA and RCC is extremely rare. Here, the authors report a 50-year-old male patient who was found to have a large cystic sellar lesion, and surgical resection revealed components of a RCC coexisting with a PA. This collision reminded us of the possibility of RCC coexisting with PA. Furthermore, a clinicopathologic relation of them were reviewed and investigated.

  6. Coexistence and specialization of pathogen strains on contact networks.

    PubMed

    Eames, Ken T D; Keeling, Matt J

    2006-08-01

    The coexistence of different pathogen strains has implications for pathogen variability and disease control and has been explained in a number of different ways. We use contact networks, which represent interactions between individuals through which infection could be transmitted, to investigate strain coexistence. For sexually transmitted diseases the structure of contact networks has received detailed study and has been shown to be a vital determinant of the epidemiological dynamics. By using analytical pairwise models and stochastic simulations, we demonstrate that network structure also has a profound influence on the interaction between pathogen strains. In particular, when the population is serially monogamous, fully cross-reactive strains can coexist, with different strains dominating in network regions with different characteristics. Furthermore, we observe specialization of different strains in different risk groups within the network, suggesting the existence of diverging evolutionary pressures.

  7. [Coexistence of coeliac disease and inflammatory bowel disease in children].

    PubMed

    Krawiec, Paulina; Pawłowska-Kamieniak, Agnieszka; Pac-Kożuchowska, Elżbieta; Mroczkowska-Juchkiewcz, Agnieszka; Kominek, Katarzyna

    2016-01-01

    Coeliac disease and inflammatory bowel disease are chronic inflammatory conditions of gastrointestinal tract with complex aetiology with genetic, environmental and immunological factors contributing to its pathogenesis. It was noted that immune-mediated disorders often coexist. There is well-known association between coeliac disease and type 1 diabetes and ulcerative colitis and primary sclerosing cholangitis. However, growing body of literature suggests the association between coeliac disease and inflammatory bowel disease, particularly ulcerative colitis. This is an extremely rare problem in paediatric gastroenterology. To date there have been reported several cases of children with coexisting coeliac disease and inflammatory bowel disease. Herewith we present review of current literature on coexistence of coeliac disease and inflammatory bowel disease in children. © 2016 MEDPRESS.

  8. A Case of hereditary spherocytosis coexisting with Gilbert's syndrome.

    PubMed

    Lee, Min Jae; Chang, Yoon Hwan; Kang, Seung Hwa; Mun, Se Kwon; Kim, Heyjin; Han, Chul Ju; Kim, Jin; Kang, Hye Jin

    2013-03-25

    We recently encountered a case of hereditary spherocytosis coexisting with Gilbert's syndrome. Patient was initially diagnosed with Gilbert's syndrome and observed, but other findings suggestive of concurrent hemolysis, such as splenomegaly and gallstones were noted during the follow-up period. Therefore, further evaluations, including a peripheral blood smear, osmotic fragility test, autohemolysis test, and red blood cell membrane protein test were performed, and coexisting hereditary spherocytosis was diagnosed. Genotyping of the conjugation enzyme uridine diphosphate-glucuronosyltransferase was used to confirm Gilbert's syndrome. Because of the high prevalence rates and similar symptoms of these 2 diseases, hereditary spherocytosis can be masked in patients with Gilbert's syndrome. In review of a case and other article, the possibility of the coexistence of these 2 diseases should be considered, especially in patients with unconjugated hyperbilirubinemia who also have splenomegaly and gallstones.

  9. Coexistence Analysis of Civil Unmanned Aircraft Systems at Low Altitudes

    NASA Astrophysics Data System (ADS)

    Zhou, Yuzhe

    2016-11-01

    The requirement of unmanned aircraft systems in civil areas is growing. However, provisioning of flight efficiency and safety of unmanned aircraft has critical requirements on wireless communication spectrum resources. Current researches mainly focus on spectrum availability. In this paper, the unmanned aircraft system communication models, including the coverage model and data rate model, and two coexistence analysis procedures, i. e. the interference and noise ratio criterion and frequency-distance-direction criterion, are proposed to analyze spectrum requirements and interference results of the civil unmanned aircraft systems at low altitudes. In addition, explicit explanations are provided. The proposed coexistence analysis criteria are applied to assess unmanned aircraft systems' uplink and downlink interference performances and to support corresponding spectrum planning. Numerical results demonstrate that the proposed assessments and analysis procedures satisfy requirements of flexible spectrum accessing and safe coexistence among multiple unmanned aircraft systems.

  10. Interdisciplinary and Cross-Cultural Perspectives on Explanatory Coexistence.

    PubMed

    Watson-Jones, Rachel E; Busch, Justin T A; Legare, Cristine H

    2015-10-01

    Natural and supernatural explanations are used to interpret the same events in a number of predictable and universal ways. Yet little is known about how variation in diverse cultural ecologies influences how people integrate natural and supernatural explanations. Here, we examine explanatory coexistence in three existentially arousing domains of human thought: illness, death, and human origins using qualitative data from interviews conducted in Tanna, Vanuatu. Vanuatu, a Melanesian archipelago, provides a cultural context ideal for examining variation in explanatory coexistence due to the lack of industrialization and the relatively recent introduction of Christianity and Western education. We argue for the integration of interdisciplinary methodologies from cognitive science and anthropology to inform research on explanatory coexistence. Copyright © 2015 Cognitive Science Society, Inc.

  11. Two interbreeding populations of Saccharomyces cerevisiae strains coexist in cachaça fermentations from Brazil.

    PubMed

    Badotti, Fernanda; Vilaça, Sibelle T; Arias, Armando; Rosa, Carlos A; Barrio, Eladio

    2014-03-01

    In this study, the phylogenetic relationships between cachaça strains of Saccharomyces cerevisiae isolated from different geographical areas in Brazil were obtained on the basis of sequences of one mitochondrial (COX2) and three nuclear (EGT2, CAT8, and BRE5) genes. This analysis allowed us to demonstrate that different types of strains coexist in cachaça fermentations: wine strains, exhibiting alleles related or identical to those present in European wine strains; native strains, containing alleles similar to those found in strains isolated from traditional fermentations from Latin America, North America, Malaysian, Japan, or West Africa; and their intraspecific hybrids or 'mestizo' strains, heterozygous for both types of alleles. Wine strains and hybrids with high proportions of wine-type alleles predominate in southern and southeastern Brazil, where cachaça production coexists with winemaking. The high frequency of 'wine-type' alleles in these regions is probably due to the arrival of wine immigrant strains introduced from Europe in the nearby wineries due to the winemaking practices. However, in north and northeastern states, regions less suited or not suited for vine growing and winemaking, wine-type alleles are much less frequent because 'mestizo' strains with intermediate or higher proportions of 'native-type' alleles are predominant.

  12. Linear shaped charge

    DOEpatents

    Peterson, David; Stofleth, Jerome H.; Saul, Venner W.

    2017-07-11

    Linear shaped charges are described herein. In a general embodiment, the linear shaped charge has an explosive with an elongated arrowhead-shaped profile. The linear shaped charge also has and an elongated v-shaped liner that is inset into a recess of the explosive. Another linear shaped charge includes an explosive that is shaped as a star-shaped prism. Liners are inset into crevices of the explosive, where the explosive acts as a tamper.

  13. Transport Properties in Nuclear Pasta

    NASA Astrophysics Data System (ADS)

    Caplan, Matthew; Horowitz, Charles; Berry, Donald; da Silva Schneider, Andre

    2016-09-01

    At the base of the inner crust of neutron stars, where matter is near the nuclear saturation density, nuclear matter arranges itself into exotic shapes such as cylinders and slabs, called `nuclear pasta.' Lepton scattering from these structures may govern the transport properties of the inner crust; electron scattering from protons in the pasta determines the thermal and electrical conductivity, as well as the shear viscosity of the inner crust. These properties may vary in pasta structures which form at various densities, temperatures, and proton fractions. In this talk, we report on our calculations of lepton transport in nuclear pasta and the implication for neutron star observables.

  14. Nuclear reactor

    DOEpatents

    Thomson, Wallace B.

    2004-03-16

    A nuclear reactor comprising a cylindrical pressure vessel, an elongated annular core centrally disposed within and spaced from the pressure vessel, and a plurality of ducts disposed longitudinally of the pressure vessel about the periphery thereof, said core comprising an annular active portion, an annular reflector just inside the active portion, and an annular reflector just outside the active a portion, said annular active portion comprising rectangular slab, porous fuel elements radially disposed around the inner reflector and extending the length of the active portion, wedge-shaped, porous moderator elements disposed adjacent one face of each fuel element and extending the length of the fuel element, the fuel and moderator elements being oriented so that the fuel elements face each other and the moderator elements do likewise, adjacent moderator elements being spaced to provide air inlet channels, and adjacent fuel elements being spaced to provide air outlet channels which communicate with the interior of the peripheral ducts, and means for introducing air into the air inlet channels which passes through the porous moderator elements and porous fuel elements to the outlet channel.

  15. Boundary of Phase Co-existence in Docosahexaenoic Acid System

    NASA Astrophysics Data System (ADS)

    Lor, Chai; Hirst, Linda S.

    2011-11-01

    Docosahexaenoic acid (DHA) is a highly polyunsaturated fatty acid (PUFA) that exhibits six double bonds in the hydrocarbon tail. It induces phase separation of the membrane into liquid order and liquid disorder in mixtures containing other lipids with more saturation and cholesterol. With the utilization of atomic force microscopy, phase co-existence is observed in lipid mixtures containing DHA on a single supported lipid bilayer. The boundary of phase co-existence with decreasing DHA concentration is explored. The elastic force, thickness, and roughness of the different phases are investigated.

  16. Coexistence and survival in conservative Lotka-Volterra networks.

    PubMed

    Knebel, Johannes; Krüger, Torben; Weber, Markus F; Frey, Erwin

    2013-04-19

    Analyzing coexistence and survival scenarios of Lotka-Volterra (LV) networks in which the total biomass is conserved is of vital importance for the characterization of long-term dynamics of ecological communities. Here, we introduce a classification scheme for coexistence scenarios in these conservative LV models and quantify the extinction process by employing the Pfaffian of the network's interaction matrix. We illustrate our findings on global stability properties for general systems of four and five species and find a generalized scaling law for the extinction time.

  17. Phase Coexistence in Gallium Nanoparticles Controlled by Electron Excitation

    NASA Astrophysics Data System (ADS)

    Pochon, S.; MacDonald, K. F.; Knize, R. J.; Zheludev, N. I.

    2004-04-01

    In gallium nanoparticles 100nm in diameter grown on the tip of an optical fiber from an atomic beam we observed equilibrium coexistence of γ, β, and liquid structural phases that can be controlled by e-beam excitation in a highly reversible and reproducible fashion. With 2keV electrons only 1pJ of excitation energy per nanoparticle is needed to exercise control, with the equilibrium phase achieved in less than a few tenths of a microsecond. The transformations between coexisting phases are accompanied by a continuous change in the nanoparticle film's reflectivity.

  18. Coexistence of ferromagnetism and singlet superconductivity via kinetic exchange.

    PubMed

    Cuoco, Mario; Gentile, Paola; Noce, Canio

    2003-11-07

    We propose a novel mechanism for the coexistence of metallic ferromagnetism and singlet superconductivity assuming that the magnetic instability is due to kinetic exchange. Within this scenario, the unpaired electrons which contribute to the magnetization have a positive feedback on the gain of the kinetic energy in the coexisting phase by undressing the effective mass of the carriers involved in the pairing. The evolution of the magnetization and pairing amplitude and the phase diagram are first analyzed for a generic kinetic exchange model and then are determined within a specific case with spin dependent bond-charge occupation.

  19. Coexistence of ferromagnetism and superconductivity in Ni/Bi bilayers.

    PubMed

    LeClair, P; Moodera, J S; Philip, J; Heiman, D

    2005-01-28

    In spite of a lack of superconductivity in bulk crystalline Bi, thin film Bi deposited on thin Ni underlayers are strong-coupled superconductors below approximately 4 K. We unambiguously demonstrate that by tuning the Ni thickness the competition between ferromagnetism and superconductivity in the Ni/Bi can be tailored. For a narrow range of Ni thicknesses, the coexistence of both a superconducting energy gap and conduction electron spin polarization are visible within the Ni side of the Ni/Bi bilayers, independent of any particular theoretical model. We believe that this represents one of the clearest observations of superconductivity and ferromagnetism coexisting.

  20. Coexistence and Survival in Conservative Lotka-Volterra Networks

    NASA Astrophysics Data System (ADS)

    Knebel, Johannes; Krüger, Torben; Weber, Markus F.; Frey, Erwin

    2013-04-01

    Analyzing coexistence and survival scenarios of Lotka-Volterra (LV) networks in which the total biomass is conserved is of vital importance for the characterization of long-term dynamics of ecological communities. Here, we introduce a classification scheme for coexistence scenarios in these conservative LV models and quantify the extinction process by employing the Pfaffian of the network’s interaction matrix. We illustrate our findings on global stability properties for general systems of four and five species and find a generalized scaling law for the extinction time.

  1. Coexistence of axial spondyloarthritis and thromboangiitis obliterans in a young woman.

    PubMed

    Lopalco, G; Iannone, F; Rigante, D; Vitale, A; Mancini, M E; Covelli, M; Lapadula, G; Cantarini, L

    2015-06-30

    A peculiar coexistence of axial spondyloarthritis and ischemia of the feet and the fourth finger of the left hand in a young woman, who was a heavy smoker, is discussed in this report. This picture was considered within the context of thromboangiitis obliterans. Positivity of anti-nuclear antibodies and mild elevation of inflammatory parameters were noted. Computed tomography angiograms of upper and lower limbs showed luminal narrowing and occlusion of the left humeral, left anterior/posterior tibial and right anterior tibial arteries. Daily iloprost perfusions were started, and smoking cessation was strongly recommended. Coldness and rest pain in the distal extremities improved within a few weeks. The possibility that spondyloarthritis might precede the clinical picture of thromboangiitis obliterans should be considered in heavy smokers.

  2. Unravelling raked linear dunes to explain the coexistence of bedforms in complex dunefields

    PubMed Central

    Lü, Ping; Narteau, Clément; Dong, Zhibao; Rozier, Olivier; Courrech du Pont, Sylvain

    2017-01-01

    Raked linear dunes keep a constant orientation for considerable distances with a marked asymmetry between a periodic pattern of semi-crescentic structures on one side and a continuous slope on the other. Here we show that this shape is associated with a steady-state dune type arising from the coexistence of two dune growth mechanisms. Primary ridges elongate in the direction of the resultant sand flux. Semi-crescentic structures result from the development of superimposed dunes growing perpendicularly to the maximum gross bedform-normal transport. In the particular case of raked linear dunes, these two mechanisms produces primary and secondary ridges with similar height but with different orientations, which are oblique to each other. The raked pattern develops preferentially on the leeward side of the primary ridges according to the direction of propagation of the superimposed bedforms. As shown by numerical modelling, raked linear dunes occur where both these oblique orientations and dynamics are met. PMID:28128195

  3. Coexistence of stable dark- and bright-soliton Kerr combs in normal-dispersion resonators

    NASA Astrophysics Data System (ADS)

    Parra-Rivas, P.; Gomila, D.; Gelens, L.

    2017-05-01

    Using the Lugiato-Lefever model, we analyze the effects of third-order chromatic dispersion on the existence and stability of dark- and bright-soliton Kerr frequency combs in the normal dispersion regime. While in the absence of third-order dispersion only dark solitons exist over an extended parameter range, we find that third-order dispersion allows for stable dark and bright solitons to coexist. Reversibility is broken and the shape of the switching waves connecting the top and bottom homogeneous solutions is modified. Bright solitons come into existence thanks to the generation of oscillations in the switching-wave profiles. Temporal oscillatory instabilities of dark solitons are suppressed in the presence of sufficiently strong third-order dispersion, while bright solitons are never found to oscillate in time. As a result of third-order dispersion both bright and dark solitons are found to move with a velocity that depends on their width.

  4. Unravelling raked linear dunes to explain the coexistence of bedforms in complex dunefields

    NASA Astrophysics Data System (ADS)

    Lü, Ping; Narteau, Clément; Dong, Zhibao; Rozier, Olivier; Courrech Du Pont, Sylvain

    2017-01-01

    Raked linear dunes keep a constant orientation for considerable distances with a marked asymmetry between a periodic pattern of semi-crescentic structures on one side and a continuous slope on the other. Here we show that this shape is associated with a steady-state dune type arising from the coexistence of two dune growth mechanisms. Primary ridges elongate in the direction of the resultant sand flux. Semi-crescentic structures result from the development of superimposed dunes growing perpendicularly to the maximum gross bedform-normal transport. In the particular case of raked linear dunes, these two mechanisms produces primary and secondary ridges with similar height but with different orientations, which are oblique to each other. The raked pattern develops preferentially on the leeward side of the primary ridges according to the direction of propagation of the superimposed bedforms. As shown by numerical modelling, raked linear dunes occur where both these oblique orientations and dynamics are met.

  5. Triple shape memory effect of star-shaped polyurethane.

    PubMed

    Yang, Xifeng; Wang, Lin; Wang, Wenxi; Chen, Hongmei; Yang, Guang; Zhou, Shaobing

    2014-05-14

    In this study, we synthesized one type of star-shaped polyurethane (SPU) with star-shaped poly(ε-caprolactone) (SPCL) containing different arm numbers as soft segment and 4,4'-diphenyl methane diisocyanate (MDI) as well as chain extender 1,4-butylene glycol (BDO) as hard segment. Proton nuclear magnetic resonance (1H-NMR) confirmed the chemical structure of the material. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) results indicated that both the melting temperature (Tm) and transition temperature (Ttrans) of SPU decreased with the hard segment composition increase. X-ray diffraction (XRD) results demonstrated that the increase of the crystallinity of SPU following the raised arm numbers endowed a high shape fixity of six-arm star-shaped polyurethane (6S-PU) and a wide melting temperature range, which resulted in an excellent triple-shape memory effect of 6S-PU. The in vitro cytotoxicity assay evaluated with osteoblasts through Alamar blue assay demonstrates that this copolymer possessed good cytocompatibility. This material can be potentially used as a new smart material in the field of biomaterials.

  6. Low-Temperature Nuclear Orientation Studies of Nuclei Far from Stability

    NASA Astrophysics Data System (ADS)

    Brown, Daniel Edward

    1990-01-01

    Available from UMI in association with The British Library. Requires signed TDF. In recent years, Low Temperature Nuclear Orientation (LTNO) has become an important technique in the study of nuclei far from stability. LTNO experiments can yield information about magnetic dipole and electric quadrupole moments and about level schemes and electromagnetic decay properties. The theory of LTNO is reviewed. Often the most interesting nuclei have short halflives (<2 hours) and must be produced "on site" by nuclear reactions before undergoing mass selection and direct implantation into cold equipment. At CERN, a new facility (NICOLE) has recently been set up at the ISOLDE -3 isotope separator and a description of this system is given. One of the major current interests in nuclear physics is to study transitional nuclei which lie between well known regions of spherical and deformed nuclei. The neutron deficient Tellurium and Iodine isotopes are examples of such nuclei. In both cases, the influence of a pi g_{9/2} intruder orbital is expected to be strong at low excitation energies and at A ~ 120. The ^ {120}Te decay scheme has been investigated in detail by LTNO supported by gamma-gamma coincidences and conversion electron spectroscopy. An interpretation of the level scheme using an IBM-2 calculation which allows for mixing between the ground state and a (4p-2h) intruder state is made. The success of this calculation provides strong evidence for the existence of the intruder configuration in ^{120}Te. In addition, the relative electric quadrupole moments of the ground states in ^{120-123}I have been measured. The absence of a measurable quadrupole moment in ^{120}I ^{g} supports the idea that this state is the spherical companion of the coexisting, well deformed pi g_{9/2} isomer. The trend in quadrupole moments also provides strong evidence for the existence of an N = 64 sub shell gap which is needed to explain the corresponding magnetic dipole moments. The light Platinum

  7. Niches and coexistence of ant communities in Puerto Rico

    Treesearch

    J.A. Torres

    1984-01-01

    I studied ant coexistence in adjacent areas of upland tropical forest, grassland, and agricultural land in San Lorenzo, Puerto Rico. Data on food utilization, daily activity, nesting sites, microhabitat utilization and interspecific aggression were collected. Ants' tolerance to 45 degree C was determined in the laboratory. Agricultural and grassland ants eat grain...

  8. Practices that support coexistence: A survey of Alfalfa growers

    USDA-ARS?s Scientific Manuscript database

    The alfalfa industry has worked hard to foster the coexistence of genetically-engineered (GE) and conventional alfalfa production by developing a set of best management practices that aim to limit adventitious-presence (AP) of GE traits in conventional seed. The general goal is to minimize transgene...

  9. Coexistence and exclusion of stochastic competitive Lotka-Volterra models

    NASA Astrophysics Data System (ADS)

    Nguyen, Dang H.; Yin, George

    2017-02-01

    This work derives sufficient conditions for the coexistence and exclusion of a stochastic competitive Lotka-Volterra model. The conditions obtained are close to necessary. In addition, convergence in distribution of positive solutions of the model is also established. A number of numerical examples are given to illustrate our results.

  10. Comorbidity: Coexisting Substance Use and Mental Disorders in Young People

    ERIC Educational Resources Information Center

    Howard, John; Stubbs, Matt; Arcuri, Anthony

    2007-01-01

    Young people with comorbid disorders (coexisting mental health and substance use disorders) present with particular issues that can be difficult for service providers, and for the community as a whole, to respond to. They tend to fall between the cracks of mental health services and substance use services, with the outcome often being ineffective…

  11. Tracking neighbours promotes the coexistence of large carnivores

    PubMed Central

    López-Bao, José Vicente; Mattisson, Jenny; Persson, Jens; Aronsson, Malin; Andrén, Henrik

    2016-01-01

    The study of competition and coexistence among similar interacting species has long been considered a cornerstone in evolutionary and community ecology. However, understanding coexistence remains a challenge. Using two similar and sympatric competing large carnivores, Eurasian lynx and wolverines, we tested the hypotheses that tracking among heterospecifics and reactive responses to potential risk decreases the probability of an agonistic encounter when predators access shared food resources, thus facilitating coexistence. Lynx and wolverines actively avoided each other, with the degree of avoidance being greater for simultaneous than time-delayed predator locations. Wolverines reacted to the presence of lynx at relatively short distances (mean: 383 m). In general, lynx stayed longer, and were more stationary, around reindeer carcasses than wolverines. However, when both predators were present at the same time around a carcass, lynx shortened their visits, while wolverine behavior did not change. Our results support the idea that risk avoidance is a reactive, rather than a predictive, process. Since wolverines have adapted to coexist with lynx, exploiting lynx-killed reindeer carcasses while avoiding potential encounters, the combined presence of both predators may reduce wolverine kill rate and thus the total impact of these predators on semi-domestic reindeer in Scandinavia. Consequently, population management directed at lynx may affect wolverine populations and human-wolverine conflicts. PMID:26979573

  12. Coexistence of chronic neutrophilic leukemia with light chain myeloma.

    PubMed

    Cehreli, C; Undar, B; Akkoc, N; Onvural, B; Altungoz, O

    1994-01-01

    A 60-year-old woman who presented with weakness, night sweats, bone pain, easy bruising and weight loss was found to have ecchymoses and hepatosplenomegaly. Blood counts showed persistent neutrophilia of mature cell type with Döhle bodies and toxic granulation. Coexistence of chronic neutrophilic leukemia and multiple myeloma of kappa light chain type was documented by bone marrow examination and immunofixation.

  13. Coexistence in a multispecies assemblage of eagles in central Asia

    USGS Publications Warehouse

    Katzner, Todd; Bragin, E.; Knick, Steven T.; Smith, Andrew T.

    2003-01-01

    We evaluated factors that permit species coexistence in an exceptional assemblage of similar raptor species at the Naurzum Zapovednik (a national nature reserve) in north-central Kazakhstan. White-tailed Sea-Eagle (Haliaeetus albicilla), Imperial Eagle (Aquila heliaca), Golden Eagle (A. chrysaetos), and Steppe Eagle (A. nipalensis) all breed at the Zapovednik. Steppe Eagle use of nesting resources was distinct from that of tree-nesting species. We evaluated differences in nest tree and nest habitat characteristics, nest dimensions and positions, and nest spacing among the three forest-dwelling eagle species to distinguish between the effects of inter- and intraspecific resource limitations on species coexistence. Although the different species bred in similar habitat and sometimes reused other species' nests, the dimensions, positions and locations of their nests often differed. These differences did not appear to result from interspecific competition. Nest spacing trends were also species specific; Imperial Eagles generally nested farther from other eagle nests than did Golden Eagles and White-tailed Sea-Eagles. Intraspecific variation in habitat, physical characteristics, and spacing patterns of Imperial Eagle nests was extensive throughout the nature reserve. Although interspecific partitioning of nesting habitat may allow coexistence of ground-nesting Steppe Eagles, interspecific competition did not appear to be a primary determinant of the use of nest habitat, space, or nests by tree-nesting species. Rather, interspecific effects appeared secondary to intraspecific effects in determining coexistence of tree-nesting eagles at this site.

  14. Climate change threatens coexistence within communities of Mediterranean forested wetlands.

    PubMed

    Di Paola, Arianna; Valentini, Riccardo; Paparella, Francesco

    2012-01-01

    The Mediterranean region is one of the hot spots of climate change. This study aims at understanding what are the conditions sustaining tree diversity in Mediterranean wet forests under future scenarios of altered hydrological regimes. The core of the work is a quantitative, dynamic model describing the coexistence of different Mediterranean tree species, typical of arid or semi-arid wetlands. Two kind of species, i.e. Hygrophilous (drought sensitive, flood resistant) and Non-hygrophilous (drought resistant, flood sensitive), are broadly defined according to the distinct adaptive strategies of trees against water stress of summer drought and winter flooding. We argue that at intermediate levels of water supply the dual role of water (resource and stress) results in the coexistence of the two kind of species. A bifurcation analysis allows us to assess the effects of climate change on the coexistence of the two species in order to highlight the impacts of predicted climate scenarios on tree diversity. Specifically, the model has been applied to Mediterranean coastal swamp forests of Central Italy located at Castelporziano Estate and Circeo National Park. Our results show that there are distinct rainfall thresholds beyond which stable coexistence becomes impossible. Regional climatic projections show that the lower rainfall threshold may be approached or crossed during the XXI century, calling for an urgent adaptation and mitigation response to prevent biodiversity losses.

  15. Coexistence of chronic paroxysmal hemicrania and benign cough headache.

    PubMed

    Mateo, I; Pascual, J

    1999-06-01

    We report on the coexistence of both chronic paroxysmal hemicrania and cough headache in a middle-aged woman. Typical chronic paroxysmal hemicrania and cough headache episodes appeared independently and responded to indomethacin. The possible pathophysiological significance of this concurrence of both types of indomethacin-responsive pain is discussed.

  16. Dual Channel Transmission for Coexistence of Wireless Networks

    DTIC Science & Technology

    2007-08-01

    DD882) Inventions (DD882) TECHNICAL REPORT W911NF-06-1-0415 Dual Channel Transmission for Coexistence of Wireless Networks September 1, 2006 – August 31...2001. [28] W. P. Osborne and M. B. Luntz, “Coherent and noncoherent detection of CPFSK,” IEEE Trans. Commmunications , vol. 22, pp. 1023–1036, Aug. 1974

  17. Coexistence facilitates interspecific biofilm formation in complex microbial communities.

    PubMed

    Madsen, Jonas S; Røder, Henriette L; Russel, Jakob; Sørensen, Helle; Burmølle, Mette; Sørensen, Søren J

    2016-09-01

    Social interactions in which bacteria respond to one another by modifying their phenotype are central determinants of microbial communities. It is known that interspecific interactions influence the biofilm phenotype of bacteria; a phenotype that is central to the fitness of bacteria. However, the underlying role of fundamental ecological factors, specifically coexistence and phylogenetic history, in biofilm formation remains unclear. This study examines how social interactions affect biofilm formation in multi-species co-cultures from five diverse environments. We found prevalence of increased biofilm formation among co-cultured bacteria that have coexisted in their original environment. Conversely, when randomly co-culturing bacteria across these five consortia, we found less biofilm induction and a prevalence of biofilm reduction. Reduction in biofilm formation was even more predominant when co-culturing bacteria from environments where long-term coexistence was unlikely to have occurred. Phylogenetic diversity was not found to be a strong underlying factor but a relation between biofilm induction and phylogenetic history was found. The data indicates that biofilm reduction is typically correlated with an increase in planktonic cell numbers, thus implying a behavioral response rather than mere growth competition. Our findings suggest that an increase in biofilm formation is a common adaptive response to long-term coexistence. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  18. Tracking the Roundup Ready® gene: implications for coexistence

    USDA-ARS?s Scientific Manuscript database

    The USDA has been conducting research to address concerns voiced by the alfalfa industry regarding the coexistence of genetically engineered and non-GE alfalfa seed production. In 2011 a survey was conducted to get a baseline estimate of the presence of transgenic roadside alfalfa plants. We surveye...

  19. Beyond Coexistence: Toward a More Reflective Religious Pluralism

    ERIC Educational Resources Information Center

    Rosenblith, Suzanne

    2008-01-01

    If a pluralistic democratic state such as the United States wishes to move beyond coexistence and toward a more reflective religious pluralism, then public schools must take epistemic issues seriously. Taking a cue from multicultural education, many have called for including the study of religion from a cultural perspective. I argue instead that,…

  20. Herbivore-induced coexistence of competing plant species.

    PubMed

    Ishii, Reiichiro; Crawley, Michael J

    2011-01-07

    We study a series of spatially implicit lottery models in which two competing plant species, with and without defensive traits, are grazed by a herbivore in a homogeneous habitat. One species (palatable) has no defensive traits, while the other (defended) has defensive traits but suffers reduced reproduction as the result of an assumed trade-off. Not surprisingly, coexistence of these plants cannot occur when the herbivore density is very low (the palatable plant always wins) or very high (the defended plant wins). At intermediate densities, however, herbivory can mediate plant coexistence, even in a homogeneous environment. If the herbivore eats several plants per bite, and its forage-selection depends on the average palatability of the plants it eats, then palatable species in the immediate neighbourhood of defended plants may be more likely to persist (associational resistance) even at higher grazing pressure. If the herbivore shows a positive numerical response to the average palatability of the habitat as a whole, then both plant populations are stabilized and coexistence is promoted, because both species obtain a minority advantage through the negative feedback caused by herbivory. If the herbivore exhibits both of these traits, the system may have at most two non-trivial equilibria, one of which is stable and the other unstable. This means that coexistence in such a system is vulnerable to large fluctuations in herbivore density and identity, and this has implications for conservation in systems where large herbivores are managed to promote plant diversity. Copyright © 2010. Published by Elsevier Ltd.

  1. Tracking neighbours promotes the coexistence of large carnivores.

    PubMed

    López-Bao, José Vicente; Mattisson, Jenny; Persson, Jens; Aronsson, Malin; Andrén, Henrik

    2016-03-16

    The study of competition and coexistence among similar interacting species has long been considered a cornerstone in evolutionary and community ecology. However, understanding coexistence remains a challenge. Using two similar and sympatric competing large carnivores, Eurasian lynx and wolverines, we tested the hypotheses that tracking among heterospecifics and reactive responses to potential risk decreases the probability of an agonistic encounter when predators access shared food resources, thus facilitating coexistence. Lynx and wolverines actively avoided each other, with the degree of avoidance being greater for simultaneous than time-delayed predator locations. Wolverines reacted to the presence of lynx at relatively short distances (mean: 383 m). In general, lynx stayed longer, and were more stationary, around reindeer carcasses than wolverines. However, when both predators were present at the same time around a carcass, lynx shortened their visits, while wolverine behavior did not change. Our results support the idea that risk avoidance is a reactive, rather than a predictive, process. Since wolverines have adapted to coexist with lynx, exploiting lynx-killed reindeer carcasses while avoiding potential encounters, the combined presence of both predators may reduce wolverine kill rate and thus the total impact of these predators on semi-domestic reindeer in Scandinavia. Consequently, population management directed at lynx may affect wolverine populations and human-wolverine conflicts.

  2. DISSEMINATED SUPERFICIAL AND WARTY TYPE OF POROKERATOSIS: A RARE COEXISTENCE

    PubMed Central

    Kanak, Kusumika; Jaiswal, A K; Reddy, Pallavi

    2011-01-01

    A 60-year-old male presented with hyperpigmented annular plaques with raised keratotic wall and central groove along with warty plaque involving the trunk and the extremities, respectively. A provisional diagnosis of porokeratosis was made which was confirmed histopathologically. Herein, we report a case of rare coexistence of disseminated superficial and warty porokeratosis. PMID:22121283

  3. Synchronized reproduction promotes species coexistence through reproductive facilitation.

    PubMed

    Chen, Yu-Yun; Hsu, Sze-Bi

    2011-04-07

    Theories for species coexistence often emphasize niche differentiation and temporal segregation of recruitment to avoid competition. Recent work on mutualism suggested that plant species sharing pollinators provide mutual facilitation when exhibit synchronized reproduction. The facilitation on reproduction may enhance species persistence and coexistence. Theoretical ecologists paid little attention to such indirect mutualistic systems by far. We propose a new model for a two-species system using difference equations. The model focuses on adult plants and assumes no resource competition between these well-established individuals. Our formulas include demographic parameters, such as mortality and recruitment rates, and functions of reproductive facilitation. Both recruitment and facilitation effects reach saturation levels when flower production is at high levels. We conduct mathematical analyses to assess conditions of coexistence. We establish demographical conditions permitting species coexistence. Our analyses suggest a "rescue" effect from a "superior" species to a "weaker" species under strong recruitment enhancement effect when the later is not self-sustainable. The facilitation on rare species may help to overcome Allee effect.

  4. Climate Change Threatens Coexistence within Communities of Mediterranean Forested Wetlands

    PubMed Central

    Di Paola, Arianna; Valentini, Riccardo; Paparella, Francesco

    2012-01-01

    The Mediterranean region is one of the hot spots of climate change. This study aims at understanding what are the conditions sustaining tree diversity in Mediterranean wet forests under future scenarios of altered hydrological regimes. The core of the work is a quantitative, dynamic model describing the coexistence of different Mediterranean tree species, typical of arid or semi-arid wetlands. Two kind of species, i.e. Hygrophilous (drought sensitive, flood resistant) and Non-hygrophilous (drought resistant, flood sensitive), are broadly defined according to the distinct adaptive strategies of trees against water stress of summer drought and winter flooding. We argue that at intermediate levels of water supply the dual role of water (resource and stress) results in the coexistence of the two kind of species. A bifurcation analysis allows us to assess the effects of climate change on the coexistence of the two species in order to highlight the impacts of predicted climate scenarios on tree diversity. Specifically, the model has been applied to Mediterranean coastal swamp forests of Central Italy located at Castelporziano Estate and Circeo National Park. Our results show that there are distinct rainfall thresholds beyond which stable coexistence becomes impossible. Regional climatic projections show that the lower rainfall threshold may be approached or crossed during the XXI century, calling for an urgent adaptation and mitigation response to prevent biodiversity losses. PMID:23077484

  5. [School coexistence and learning in adolescence from a gender perspective].

    PubMed

    Díaz-Aguado Jalón, María José; Martín Seoane, Gema

    2011-04-01

    This article reviews recent research about academic learning and school coexistence in adolescence from a gender perspective. It focuses on the research developed by the Preventive Psychology research group (UCM), specially the results from the Spanish National Study of School Coexistence using a sample of 22,247 secondary school students. Research shows that girls are overrepresented in positive indicators whereas boys are in negative indicators, not only in academic adjustment but also in school coexistence. Girls' better academic achievement can be explained by their higher tendency to overcome sexism: they identify with traditional masculinity values (such as success orientation) without giving up traditional femininity values (such as empathy). Based on this, the following conclusions are reached: 1) to extend the advantages of equality also to men; 2) to emphasize that sharing academic contexts and activities is necessary but sufficient to construct equality; and lastly, 3) to improve school coexistence, it is necessary to adopt a integrative gender approach to prevent any kind of violence, including violence against women.

  6. Quantum Controlled Nuclear Fusion

    NASA Astrophysics Data System (ADS)

    Gruebele, Martin

    2017-06-01

    Laser-assisted nuclear fusion is a potential means for providing short, well-controlled particle bursts in the lab, such as neutron or alpha particle pulses. I will discuss computational results of how coherent control by shaped, amplified 800 nm laser pulses can be used to enhance the nuclear fusion cross section of diatomic molecules such as BH or DT. Quantum dynamics simulations show that a strong laser pulse can simultaneously field-bind the diatomic molecule after electron ejection, and increase the amplitude of the vibrational wave function at small internuclear distances. When VUV shaped laser pulses become available, coherent laser control may also be extended to muonic molecules such as D-mu-T, held together by muons instead of electrons. Muonic fusion has been extensively investigated for many decades, but without coherent laser control it falls slightly short of the break-evne point.

  7. Nuclear deterrence and disarmament after the Cold War

    SciTech Connect

    Lehman, R.F. II

    1995-03-01

    During the Cold War, nuclear arms control measures were shaped significantly by nuclear doctrine. Consequently, the negotiation of arms control agreements often became a battleground for different nuclear strategies. The Cold War between the United States and the Soviet Union has been declared over. Today, both nuclear weapons policies and arms control objectives are again being reviewed. This document discusses points of this review.

  8. Similarity law for Widom lines and coexistence lines

    NASA Astrophysics Data System (ADS)

    Banuti, D. T.; Raju, M.; Ihme, M.

    2017-05-01

    The coexistence line of a fluid separates liquid and gaseous states at subcritical pressures, ending at the critical point. Only recently, it became clear that the supercritical state space can likewise be divided into regions with liquidlike and gaslike properties, separated by an extension to the coexistence line. This crossover line is commonly referred to as the Widom line, and is characterized by large changes in density or enthalpy, manifesting as maxima in the thermodynamic response functions. Thus, a reliable representation of the coexistence line and the Widom line is important for sub- and supercritical applications that depend on an accurate prediction of fluid properties. While it is known for subcritical pressures that nondimensionalization with the respective species critical pressures pcr and temperatures Tcr only collapses coexistence line data for simple fluids, this approach is used for Widom lines of all fluids. However, we show here that the Widom line does not adhere to the corresponding states principle, but instead to the extended corresponding states principle. We resolve this problem in two steps. First, we propose a Widom line functional based on the Clapeyron equation and derive an analytical, species specific expression for the only parameter from the Soave-Redlich-Kwong equation of state. This parameter is a function of the acentric factor ω and compares well with experimental data. Second, we introduce the scaled reduced pressure pr* to replace the previously used reduced pressure pr=p /pcr . We show that pr* is a function of the acentric factor only and can thus be readily determined from fluid property tables. It collapses both subcritical coexistence line and supercritical Widom line data over a wide range of species with acentric factors ranging from -0.38 (helium) to 0.34 (water), including alkanes up to n-hexane. By using pr*, the extended corresponding states principle can be applied within corresponding states principle

  9. [Coexistence of Addison-Biermer's anaemia with endocrine glands' dysfunctions].

    PubMed

    Kuliszkiewicz-Janus, Malgorzata; Bednarek-Tupikowska, Grazyna; Rózycka, Beata; Dereń, Izabela

    2004-11-01

    Addison-Biermer's anaemia is an autoimmune disease. It may coexist with other auto-aggressive diseases, precede them or join the other existing autoimmune diseases. It most often accompanies the Hashimoto disease but also may coexist polyglandular autoimmune syndrome (PGA). Three types of PGA are distinguished: PGA1--Blizzard's Syndrome, PGA2--Schmidt's Syndrome, and PGA3. The latter, unlike the remaining ones, is characterized by normal function of adrenal glands. Addison-Biermer's anaemia occurrence may be often difficult to diagnose as coexisting illnesses might ouflage its clinical symptoms. The aim of this paper was to analyse patients with different types of PGA with coexisting Addison-Biermer's anaemia. Group of 24 individuals was analysed: 2 women with PGA1, 10 patients with PGA2, 10 patients with PGA3. In 2 remaining ones PGA was not confirmed. Addison-Biermer's anaemia occurred in 7 patients (2 with PGA2 and 5 with PGA3 syndrome). Decreased concentration of vitamin B12 was diagnosed in 3 individuals among 24 examined patients (1 with type 3 and 2 with type 2), as well in 2 patients with unconfirmed PGA. Addison-Biermer's anaemia was not observed in patients with PGA1. We observed that megaloblastic anaemia occurred characteristic schedule depending on appearance of autoimmune diseases: in PGA2--many years after other immunopathies were found, in PGA3--as first auto-aggressive disease. Our analysis suggests the necessity of detailed check-ups on patients with Addison-Biermer's anaemia, as with time they may develop other diseases, especially hypothyroidism and/or PGA failure. On the contrary, in individuals with thyroid gland diseases and PGA syndromes further checkups should be megaloblastic anaemia-sensitive. In both cases it is important to consider substitutive treatment. The possibility of family coexisting both pernicious anaemia and autoimmune endocrinopathies needs diagnostics of members of the patient's family.

  10. Nuclear Chemistry.

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1979

    1979-01-01

    Provides a brief review of the latest developments in nuclear chemistry. Nuclear research today is directed toward increased activity in radiopharmaceuticals and formation of new isotopes by high-energy, heavy-ion collisions. (Author/BB)

  11. Nuclear Scans

    MedlinePlus

    Nuclear scans use radioactive substances to see structures and functions inside your body. They use a special ... images. Most scans take 20 to 45 minutes. Nuclear scans can help doctors diagnose many conditions, including ...

  12. Nuclear Winter.

    ERIC Educational Resources Information Center

    Ehrlich, Anne

    1984-01-01

    "Nuclear Winter" was recently coined to describe the climatic and biological effects of a nuclear war. These effects are discussed based on models, simulations, scenarios, and projections. Effects on human populations are also considered. (JN)

  13. Nuclear Medicine

    MedlinePlus

    ... Home » Science Education » Science Topics » Nuclear Medicine SCIENCE EDUCATION SCIENCE EDUCATION Science Topics Resource Links for General Public Resource ... Related Documents: Nuclear Medicine Fact Sheet.pdf SCIENCE EDUCATION Science Topics Resource Links for General Public Resource ...

  14. Nuclear Chemistry.

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1979

    1979-01-01

    Provides a brief review of the latest developments in nuclear chemistry. Nuclear research today is directed toward increased activity in radiopharmaceuticals and formation of new isotopes by high-energy, heavy-ion collisions. (Author/BB)

  15. Nuclear Winter.

    ERIC Educational Resources Information Center

    Ehrlich, Anne

    1984-01-01

    "Nuclear Winter" was recently coined to describe the climatic and biological effects of a nuclear war. These effects are discussed based on models, simulations, scenarios, and projections. Effects on human populations are also considered. (JN)

  16. Experimental investigations on the nuclear structure of the neutron-rich nuclides 44S and 20O

    NASA Astrophysics Data System (ADS)

    Santiago-Gonzalez, Daniel

    Experimental results of two independent studies on the nuclear structure of the neutron-rich nuclei S4416 and O20 8 O are presented. A short introduction on the context of these studies within nuclear physics is given in chapter 1. Because of the fundamental differences between the experiments and analysis techniques the investigations have been separated in two chapters. The investigation of 44S, extracted via the two-proton knockout reaction from 46Ar with intermediate beam energy, is presented in chapter 2. Four new excited states are identified, of which the first 4+ state presents evidence of deformation, as suggested by line-shape simulations of the detected gamma rays. This is also indicated by a shell-model calculation, where the deformation of the first 4 + state originates in a neutron particle-hole configuration which is fundamentally different from the "intruder"configuration producing the ground state deformation and from the configuration describing the relatively long-lived isomeric 0+ state. Consequently, not three coexisting shapes, rather three coexisting configurations are found in 44S, corresponding to zero, one and two neutron particle-hole excitations. In chapter 3, results from the analysis of the 19O( d,p)20O reaction in inverse kinematics using the active gas target detector array ANASEN are presented. In order to study the location and fragmentation of the d3/2 orbital in 20O, a beam of the short-lived 19O was produced at the RESOLUT radioactive beam facility of the Florida State University. The ejected protons from the (d,p) reaction were measured with large solid angle coverage and for beam energies between 2.2 and 4.3 MeV/A. Data from the 17O(d,p)18O reaction was acquired to verify our experimental methods and analysis techniques.

  17. Nuclear weapons, nuclear effects, nuclear war

    SciTech Connect

    Bing, G.F.

    1991-08-20

    This paper provides a brief and mostly non-technical description of the militarily important features of nuclear weapons, of the physical phenomena associated with individual explosions, and of the expected or possible results of the use of many weapons in a nuclear war. Most emphasis is on the effects of so-called ``strategic exchanges.``

  18. Nuclear Fuels.

    ERIC Educational Resources Information Center

    Nash, J. Thomas

    1983-01-01

    Trends in and factors related to the nuclear industry and nuclear fuel production are discussed. Topics addressed include nuclear reactors, survival of the U.S. uranium industry, production costs, budget cuts by the Department of Energy and U.S. Geological survey for resource studies, mining, and research/development activities. (JN)

  19. Nuclear Fuels.

    ERIC Educational Resources Information Center

    Nash, J. Thomas

    1983-01-01

    Trends in and factors related to the nuclear industry and nuclear fuel production are discussed. Topics addressed include nuclear reactors, survival of the U.S. uranium industry, production costs, budget cuts by the Department of Energy and U.S. Geological survey for resource studies, mining, and research/development activities. (JN)

  20. Coexisting static magnetic ordering and superconductivity in CeCu2.1Si2 found by muon spin relaxation

    NASA Technical Reports Server (NTRS)

    Uemura, Y. J.; Kossler, W. J.; Yu, X. H.; Schone, H. E.; Kempton, J. R.; Stronach, C. E.; Barth, S.; Gygax, F. N.; Hitti, B.; Schenck, A.

    1988-01-01

    Zero- and longitudinal-field muon spin relaxation measurements on a heavy fermion system CeCu2.1 Si2 have revealed an onset of static magnetic ordering below T(M) approximately 0.8 K, which coexists with superconductivity below T(c) = 0.7 K. The line shapes of the observed muon spin depolarization functions suggest an ordering in either spin glass or incommensurate spin-density-wave state, with a small averaged static moment of the order of 0.1 micro-B per formula unit at T approaches 0.

  1. Inner/Outer Nuclear Membrane Fusion in Nuclear Pore Assembly

    PubMed Central

    Fichtman, Boris; Ramos, Corinne; Rasala, Beth; Harel, Amnon

    2010-01-01

    Nuclear pore complexes (NPCs) are large proteinaceous channels embedded in double nuclear membranes, which carry out nucleocytoplasmic exchange. The mechanism of nuclear pore assembly involves a unique challenge, as it requires creation of a long-lived membrane-lined channel connecting the inner and outer nuclear membranes. This stabilized membrane channel has little evolutionary precedent. Here we mapped inner/outer nuclear membrane fusion in NPC assembly biochemically by using novel assembly intermediates and membrane fusion inhibitors. Incubation of a Xenopus in vitro nuclear assembly system at 14°C revealed an early pore intermediate where nucleoporin subunits POM121 and the Nup107-160 complex were organized in a punctate pattern on the inner nuclear membrane. With time, this intermediate progressed to diffusion channel formation and finally to complete nuclear pore assembly. Correct channel formation was blocked by the hemifusion inhibitor lysophosphatidylcholine (LPC), but not if a complementary-shaped lipid, oleic acid (OA), was simultaneously added, as determined with a novel fluorescent dextran-quenching assay. Importantly, recruitment of the bulk of FG nucleoporins, characteristic of mature nuclear pores, was not observed before diffusion channel formation and was prevented by LPC or OA, but not by LPC+OA. These results map the crucial inner/outer nuclear membrane fusion event of NPC assembly downstream of POM121/Nup107-160 complex interaction and upstream or at the time of FG nucleoporin recruitment. PMID:20926687

  2. Nuclear Parton Distribution Functions

    SciTech Connect

    Schienbein, I.; Yu, J.-Y.; Keppel, Cynthia; Morfin, Jorge; Olness, F.; Owens, J.F.

    2009-01-01

    We study nuclear effects of charged current deep inelastic neutrino-iron scattering in the framework of a chi^2 analysis of parton distribution functions (PDFs). We extract a set of iron PDFs which are used to compute x_Bj-dependent and Q^2-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged-lepton--iron scattering. We find that, except for very high x_Bj, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.

  3. Nuclear Parton Distribution Functions

    SciTech Connect

    I. Schienbein, J.Y. Yu, C. Keppel, J.G. Morfin, F. Olness, J.F. Owens

    2009-06-01

    We study nuclear effects of charged current deep inelastic neutrino-iron scattering in the framework of a {chi}{sup 2} analysis of parton distribution functions (PDFs). We extract a set of iron PDFs which are used to compute x{sub Bj}-dependent and Q{sup 2}-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged-lepton--iron scattering. We find that, except for very high x{sub Bj}, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.

  4. Shape-Shifting Plastic

    SciTech Connect

    2015-05-20

    A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature

  5. Nuclear orientation and nuclear structure

    SciTech Connect

    Krane, K.S.

    1988-01-01

    The present generation of on-line nuclear orientation facilities promises to revolutionize the gathering of nuclear structure information, especially for the hitherto poorly known and understood nuclei far from stability. Following a brief review of the technological developments that have facilitated these experiments, the nuclear spectroscopic information that can be obtained is summarized. Applications to understanding nuclear structure are reviewed, and challenges for future studies are discussed. 14 refs., 4 figs., 3 tabs.

  6. Processing multidimensional nuclear physics data

    SciTech Connect

    Becker, J.

    1994-11-15

    Modern Ge detector arrays for gamma-ray spectroscopy are producing data sets unprecedented in size and event multiplicity. Gammasphere, the DOE sponsored array, has the following characteristics: (1) High granularity (110 detectors); (2) High efficiency (10%); and (3) Precision energy measurements (Delta EE = 0.2%). Characteristics of detector line shape, the data set, and the standard practice in the nuclear physics community to the nuclear gamma-ray cascades from the 4096 times 4096 times 4096 data cube will be discussed.

  7. Nuclear networking.

    PubMed

    Xie, Wei; Burke, Brian

    2017-07-04

    Nuclear lamins are intermediate filament proteins that represent important structural components of metazoan nuclear envelopes (NEs). By combining proteomics and superresolution microscopy, we recently reported that both A- and B-type nuclear lamins form spatially distinct filament networks at the nuclear periphery of mouse fibroblasts. In particular, A-type lamins exhibit differential association with nuclear pore complexes (NPCs). Our studies reveal that the nuclear lamina network in mammalian somatic cells is less ordered and more complex than that of amphibian oocytes, the only other system in which the lamina has been visualized at high resolution. In addition, the NPC component Tpr likely links NPCs to the A-type lamin network, an association that appears to be regulated by C-terminal modification of various A-type lamin isoforms. Many questions remain, however, concerning the structure and assembly of lamin filaments, as well as with their mode of association with other nuclear components such as peripheral chromatin.

  8. Analysis of potential factors allowing coexistence in a sexual/asexual minnow complex.

    PubMed

    Barron, James N; Lawson, Troy J; Jensen, Philip A

    2016-03-01

    The northern redbelly dace (Chrosomus eos) and the finescale dace (C. neogaeus) have hybridized to produce an all-female, asexual hybrid (C. eos-neogaeus) that reproduces by sperm-limited parthenogenesis (gynogenesis). However, in this system, gynogenesis is not 100 % efficient; triploid females are occasionally formed which reproduce as sexuals, producing nuclear males and females of the paternal species (generally C. eos). Thus, the asexual lineage continually produces occasional males that can serve as a sperm source. Because (almost) all hybrid offspring are females, the hybrid population has the potential to grow more quickly and even outcompete the sexuals, thus eliminating their own sperm source. The current research uses behavioral testing, ovarian analyses, and modeling to examine three hypotheses for the maintenance of the sexual/asexual complex: male discrimination against hybrid females, fecundity differences between sexual and asexual females, and production of nuclear male sexuals from the asexual lineage. Results suggest that males do not discriminate against asexual females, and that both sexual and asexual females have similar fecundities, eliminating these hypotheses as potential coexistence mechanisms. However, computer simulations of population growth support the hypothesis that occasional triploidy within the hybrid population supplies enough breeding males to maintain the sexual/asexual complex.

  9. What Coexists with the Ferromagnetic Metallic Phase in Manganites?

    SciTech Connect

    Burkhardt, Mark H; Hossain, M A; Sarkar, S; Achkar, A J; Hawthorn, D G; Sutarto, R; Chuang, 5 Y.-D.; Gonzalez, A G Cruz; Choi, Y J; Cheong, S -W; Durr, H A; Stohr, J

    2012-07-25

    Colossal magnetoresistance, whereby the application of a magnetic field reduces the resistivity of a manganite by orders of magnitude, is generally believed to occur because of coexisting phases. Development of a complete theory to explain the phenomenon requires that the exact nature of these phases be known. We used resonant elastic soft x-ray scattering to examine the superlattice order that exists in La{sub 0.35}Pr{sub 0.275}Ca{sub 0.375}MnO{sub 3} above and below the Curie temperature. By measuring the resonance profile of the scattered x-rays at different values of q, we disentangle the contributions of orbital order and antiferromagnetism to the scattering signal above the Curie temperature. Below the Curie temperature, we see no signal from orbital order, and only antiferromagnetism coexists with the dominant ferromagnetic metallic phase.

  10. Uni-directional interaction and plant-pollinator-robber coexistence.

    PubMed

    Wang, Yuanshi; DeAngelis, Donald L; Holland, J Nathaniel

    2012-09-01

    A mathematical model for the plant-pollinator-robber interaction is studied to understand the factors leading to the widespread occurrence and stability of such interactions. In the interaction, a flowering plant provides resource for its pollinator and the pollinator has both positive and negative effects on the plant. A nectar robber acts as a plant predator, consuming a common resource with the pollinator, but with a different functional response. Using dynamical systems theory, mechanisms of species coexistence are investigated to show how a robber could invade the plant-pollinator system and persist stably with the pollinator. In addition, circumstances are demonstrated in which the pollinator's positive and negative effects on the plant could determine the robber's invasibility and the three-species coexistence.

  11. Community assembly and coexistence in communities of arbuscular mycorrhizal fungi

    PubMed Central

    Vályi, Kriszta; Mardhiah, Ulfah; Rillig, Matthias C; Hempel, Stefan

    2016-01-01

    Arbuscular mycorrhizal fungi are asexual, obligately symbiotic fungi with unique morphology and genomic structure, which occupy a dual niche, that is, the soil and the host root. Consequently, the direct adoption of models for community assembly developed for other organism groups is not evident. In this paper we adapted modern coexistence and assembly theory to arbuscular mycorrhizal fungi. We review research on the elements of community assembly and coexistence of arbuscular mycorrhizal fungi, highlighting recent studies using molecular methods. By addressing several points from the individual to the community level where the application of modern community ecology terms runs into problems when arbuscular mycorrhizal fungi are concerned, we aim to account for these special circumstances from a mycocentric point of view. We suggest that hierarchical spatial structure of arbuscular mycorrhizal fungal communities should be explicitly taken into account in future studies. The conceptual framework we develop here for arbuscular mycorrhizal fungi is also adaptable for other host-associated microbial communities. PMID:27093046

  12. Dynamical Scaling and Phase Coexistence in Topologically Constrained DNA Melting

    NASA Astrophysics Data System (ADS)

    Fosado, Y. A. G.; Michieletto, D.; Marenduzzo, D.

    2017-09-01

    There is a long-standing experimental observation that the melting of topologically constrained DNA, such as circular closed plasmids, is less abrupt than that of linear molecules. This finding points to an important role of topology in the physics of DNA denaturation, which is, however, poorly understood. Here, we shed light on this issue by combining large-scale Brownian dynamics simulations with an analytically solvable phenomenological Landau mean field theory. We find that the competition between melting and supercoiling leads to phase coexistence of denatured and intact phases at the single-molecule level. This coexistence occurs in a wide temperature range, thereby accounting for the broadening of the transition. Finally, our simulations show an intriguing topology-dependent scaling law governing the growth of denaturation bubbles in supercoiled plasmids, which can be understood within the proposed mean field theory.

  13. Controlling coexisting attractors of an impacting system via linear augmentation

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Páez Chávez, Joseph

    2017-06-01

    This paper studies the control of coexisting attractors in an impacting system via a recently developed control law based on linear augmentation. Special attention is given to two control issues in the framework of multistable engineering systems, namely, the switching between coexisting attractors without altering the system's main parameters and the avoidance of grazing-induced chaotic responses. The effectiveness of the proposed control scheme is confirmed numerically for the case of a periodically excited, soft impact oscillator. Our analysis shows how path-following techniques for non-smooth systems can be used in order to determine the optimal control parameters in terms of energy expenditure due to the control signal and transient behavior of the control error, which can be applied to a broad range of engineering problems.

  14. Coexistence of multiple metastable polytypes in rhombohedral bismuth

    PubMed Central

    Shu, Yu; Hu, Wentao; Liu, Zhongyuan; Shen, Guoyin; Xu, Bo; Zhao, Zhisheng; He, Julong; Wang, Yanbin; Tian, Yongjun; Yu, Dongli

    2016-01-01

    Derivative structural polytypes coexisting with the rhombohedral A7 structure of elemental bismuth (Bi) have been discovered at ambient condition, based on microstructure analyses of pure Bi samples treated under high pressure and high temperature conditions. Three structures with atomic positions close to those of the A7 structure have been identified through first-principles calculations, showing these polytypes energetically comparable to the A7 structure under ambient condition. Simulated diffraction data are in excellent agreement with the experimental observations. We argue that previously reported some variations of physical properties (e.g., density, electrical conductivity, and magnetism) in bismuth could be due to the formation of these polytypes. The coexistence of metastable derivative structural polytypes may be a widely occurring phenomenon in other elemental materials. PMID:26883895

  15. Geometric constraints on phase coexistence in vanadium dioxide single crystals

    NASA Astrophysics Data System (ADS)

    McGahan, Christina; Gamage, Sampath; Liang, Jiran; Cross, Brendan; Marvel, Robert E.; Haglund, Richard F.; Abate, Yohannes

    2017-02-01

    The appearance of stripe phases is a characteristic signature of strongly correlated quantum materials, and its origin in phase-changing materials has only recently been recognized as the result of the delicate balance between atomic and mesoscopic materials properties. A vanadium dioxide (VO2) single crystal is one such strongly correlated material with stripe phases. Infrared nano-imaging on low-aspect-ratio, single-crystal VO2 microbeams decorated with resonant plasmonic nanoantennas reveals a novel herringbone pattern of coexisting metallic and insulating domains intercepted and altered by ferroelastic domains, unlike previous reports on high-aspect-ratio VO2 crystals where the coexisting metal/insulator domains appear as alternating stripe phases perpendicular to the growth axis. The metallic domains nucleate below the crystal surface and grow towards the surface with increasing temperature as suggested by the near-field plasmonic response of the gold nanorod antennas.

  16. The coexistence of renal artery stenosis and pheochromocytoma.

    PubMed Central

    Hill, F S; Jander, H P; Murad, T; Diethelm, A G

    1983-01-01

    The coexistence of renal artery stenosis and pheochromocytoma has been recognized since 1958 and a total of 36 patients reported. This article provides an additional patient with an extra adrenal pheochromocytoma and fibrous bands constricting the left renal artery. Hypertension was confirmed to occur from both excess catecholamine production and hyperreninemia from the left kidney. Surgical removal of the functioning paraganglioma and correction of the renal artery stenosis restored the postoperative plasma catecholamine, renin, and blood pressure to normal. A literature review confirmed the coexistence of these two lesions but failed to provide a common etiology to explain the pathophysiology encountered. However, when the two diseases occur simultaneously, both must be diagnosed accurately and treated in a definitive manner. Images Figs. 1a and b. Figs. 2a and b. PMID:6830355

  17. Coexistence of tunneling magnetoresistance and Josephson effects in SFIFS junctions

    NASA Astrophysics Data System (ADS)

    Vávra, O.; Soni, R.; Petraru, A.; Himmel, N.; Vávra, I.; Fabian, J.; Kohlstedt, H.; Strunk, Ch.

    2017-02-01

    We demonstrate an integration of tunneling magnetoresistance and the Josephson effects within one tunneling junction. Several sets of Nb-Fe-Al-Al2O3-Fe-Nb wafers with varying Al and Fe layers thickness were prepared to systematically explore the competition of TMR and Josephson effects. A coexistence of the critical current IC(dFe) and the tunneling magnetoresistance ratio T M R(dFe) is observed for iron layer dFe thickness range 1.9 and 2.9 nm. Further optimization such as thinner Al2O3 layer leads to an enhancement of the critical current and thus to an extension of the coexistence regime up to dFe≃3.9 nm Fe.

  18. Coexistence of superconductivity and magnetism by chemical design.

    PubMed

    Coronado, Eugenio; Martí-Gastaldo, Carlos; Navarro-Moratalla, Efrén; Ribera, Antonio; Blundell, Stephen J; Baker, Peter J

    2010-12-01

    Although the coexistence of superconductivity and ferromagnetism in one compound is rare, some examples of such materials are known to exist. Methods to physically prepare hybrid structures with both competing phases are also known, which rely on the nanofabrication of alternating conducting layers. Chemical methods of building up hybrid materials with organic molecules (superconducting layers) and metal complexes (magnetic layers) have provided examples of superconductivity with some magnetic properties, but not fully ordered. Now, we report a chemical design strategy that uses the self assembly in solution of macromolecular nanosheet building blocks to engineer the coexistence of superconductivity and magnetism in [Ni(0.66)Al(0.33)(OH)(2)][TaS(2)] at ∼4 K. The method is further demonstrated in the isostructural [Ni(0.66)Fe(0.33)(OH)(2)][TaS(2)], in which the magnetic ordering is shifted from 4 K to 16 K.

  19. Coexistence of superconductivity and ferromagnetism in two dimensions.

    PubMed

    Dikin, D A; Mehta, M; Bark, C W; Folkman, C M; Eom, C B; Chandrasekhar, V

    2011-07-29

    Ferromagnetism is usually considered to be incompatible with conventional superconductivity, as it destroys the singlet correlations responsible for the pairing interaction. Superconductivity and ferromagnetism are known to coexist in only a few bulk rare-earth materials. Here we report evidence for their coexistence in a two-dimensional system: the interface between two bulk insulators, LaAlO(3) (LAO) and SrTiO(3) (STO), a system that has been studied intensively recently. Magnetoresistance, Hall, and electric-field dependence measurements suggest that there are two distinct bands of charge carriers that contribute to the interface conductivity. The sensitivity of properties of the interface to an electric field makes this a fascinating system for the study of the interplay between superconductivity and magnetism.

  20. Geometric constraints on phase coexistence in vanadium dioxide single crystals.

    PubMed

    McGahan, Christina; Gamage, Sampath; Liang, Jiran; Cross, Brendan; Marvel, Robert E; Haglund, Richard F; Abate, Yohannes

    2017-02-24

    The appearance of stripe phases is a characteristic signature of strongly correlated quantum materials, and its origin in phase-changing materials has only recently been recognized as the result of the delicate balance between atomic and mesoscopic materials properties. A vanadium dioxide (VO2) single crystal is one such strongly correlated material with stripe phases. Infrared nano-imaging on low-aspect-ratio, single-crystal VO2 microbeams decorated with resonant plasmonic nanoantennas reveals a novel herringbone pattern of coexisting metallic and insulating domains intercepted and altered by ferroelastic domains, unlike previous reports on high-aspect-ratio VO2 crystals where the coexisting metal/insulator domains appear as alternating stripe phases perpendicular to the growth axis. The metallic domains nucleate below the crystal surface and grow towards the surface with increasing temperature as suggested by the near-field plasmonic response of the gold nanorod antennas.

  1. Community assembly and coexistence in communities of arbuscular mycorrhizal fungi.

    PubMed

    Vályi, Kriszta; Mardhiah, Ulfah; Rillig, Matthias C; Hempel, Stefan

    2016-10-01

    Arbuscular mycorrhizal fungi are asexual, obligately symbiotic fungi with unique morphology and genomic structure, which occupy a dual niche, that is, the soil and the host root. Consequently, the direct adoption of models for community assembly developed for other organism groups is not evident. In this paper we adapted modern coexistence and assembly theory to arbuscular mycorrhizal fungi. We review research on the elements of community assembly and coexistence of arbuscular mycorrhizal fungi, highlighting recent studies using molecular methods. By addressing several points from the individual to the community level where the application of modern community ecology terms runs into problems when arbuscular mycorrhizal fungi are concerned, we aim to account for these special circumstances from a mycocentric point of view. We suggest that hierarchical spatial structure of arbuscular mycorrhizal fungal communities should be explicitly taken into account in future studies. The conceptual framework we develop here for arbuscular mycorrhizal fungi is also adaptable for other host-associated microbial communities.

  2. Phase coexistence in the mixed crystal Rb[sub 1-x](NH[sub 4])[sub x]H[sub 2]AsO[sub 4

    SciTech Connect

    Pinto, N.J.

    1992-01-01

    A study of the coexistence phenomenon in mixed crystals of rubidium ammonium dihydrogen arsenate has been done. Coexistence in this study refers to the simultaneous presence of ferroelectric and proton glass phases as temperature is lowered below the ferroelectric phase transition temperature T[sub c]. Such coexistence is found to exist in these mixed crystals only for small ammonium concentrations. The results show that coexistence exists for lower ammonium concentration than previously suggested. A study was also done on crystals with larger ammonium concentrations that show pure proton glass behavior and the results compared with the coexistence phenomenon. Dielectric, spontaneous polarization and nuclear magnetic resonance experiments on mixed crystals with small ammonium concentrations show that at low temperatures there exists intimate coexistence of ferroelectric clusters with proton glass clusters below the glass transition temperature T[sub g]. In the proton glass phase, it is observed that a spread of relaxation times due to the creation and annihilation of HAsO[sub 4] and H[sub 3]AsO[sub 4] pairs as they diffuse through the crystal. Spin lattice relaxation times for the acid deuterons in a 10% ammoniated sample show a broad T[sub 1] minimum near the glass transition temperature which is characteristic of proton glasses. Field-cooling experiments were also done on the pure proton glass. The results are consistent with dielectric measurements, but the remanent polarization was found to be extremely small. This polarization was found to depend on the rate of heating and cooling the sample while performing the experiment.

  3. Coexistence between wildlife and humans at fine spatial scales

    PubMed Central

    Carter, Neil H.; Shrestha, Binoj K.; Karki, Jhamak B.; Pradhan, Narendra Man Babu; Liu, Jianguo

    2012-01-01

    Many wildlife species face imminent extinction because of human impacts, and therefore, a prevailing belief is that some wildlife species, particularly large carnivores and ungulates, cannot coexist with people at fine spatial scales (i.e., cannot regularly use the exact same point locations). This belief provides rationale for various conservation programs, such as resettling human communities outside protected areas. However, quantitative information on the capacity and mechanisms for wildlife to coexist with humans at fine spatial scales is scarce. Such information is vital, because the world is becoming increasingly crowded. Here, we provide empirical information about the capacity and mechanisms for tigers (a globally endangered species) to coexist with humans at fine spatial scales inside and outside Nepal’s Chitwan National Park, a flagship protected area for imperiled wildlife. Information obtained from field cameras in 2010 and 2011 indicated that human presence (i.e., people on foot and vehicles) was ubiquitous and abundant throughout the study site; however, tiger density was also high. Surprisingly, even at a fine spatial scale (i.e., camera locations), tigers spatially overlapped with people on foot and vehicles in both years. However, in both years, tigers offset their temporal activity patterns to be much less active during the day when human activity peaked. In addition to temporal displacement, tiger–human coexistence was likely enhanced by abundant tiger prey and low levels of tiger poaching. Incorporating fine-scale spatial and temporal activity patterns into conservation plans can help address a major global challenge—meeting human needs while sustaining wildlife. PMID:22949642

  4. Coexistence analysis of diploid and triploid hybrid water frogs

    NASA Astrophysics Data System (ADS)

    Apri, M.; Suandi, D.; Soewono, E.

    2014-02-01

    A dynamical model for genotype distributions of all hybrid populations of Pelophylax esculentus in the absence of differential survival is studied here. Assuming that under natural condition the parental genotypes LL and RR do not survive into adult stage, the dynamic is then reduced into three-dimensional dynamical system of classes LR, LLR, LRR genotypes. Coexistence of diploid (LR) and triploid (LLR and LRR) genotypes is analyzed here.

  5. Auditory-olfactory synesthesia coexisting with auditory-visual synesthesia.

    PubMed

    Jackson, Thomas E; Sandramouli, Soupramanien

    2012-09-01

    Synesthesia is an unusual condition in which stimulation of one sensory modality causes an experience in another sensory modality or when a sensation in one sensory modality causes another sensation within the same modality. We describe a previously unreported association of auditory-olfactory synesthesia coexisting with auditory-visual synesthesia. Given that many types of synesthesias involve vision, it is important that the clinician provide these patients with the necessary information and support that is available.

  6. Multitrait successional forest dynamics enable diverse competitive coexistence.

    PubMed

    Falster, Daniel S; Brännström, Åke; Westoby, Mark; Dieckmann, Ulf

    2017-03-10

    To explain diversity in forests, niche theory must show how multiple plant species coexist while competing for the same resources. Although successional processes are widespread in forests, theoretical work has suggested that differentiation in successional strategy allows only a few species stably to coexist, including only a single shade tolerant. However, this conclusion is based on current niche models, which encode a very simplified view of plant communities, suggesting that the potential for niche differentiation has remained unexplored. Here, we show how extending successional niche models to include features common to all vegetation-height-structured competition for light under a prevailing disturbance regime and two trait-mediated tradeoffs in plant function-enhances the diversity of species that can be maintained, including a diversity of shade tolerants. We identify two distinct axes of potential niche differentiation, corresponding to the traits leaf mass per unit leaf area and height at maturation. The first axis allows for coexistence of different shade tolerances and the second axis for coexistence among species with the same shade tolerance. Addition of this second axis leads to communities with a high diversity of shade tolerants. Niche differentiation along the second axis also generates regions of trait space wherein fitness is almost equalized, an outcome we term "evolutionarily emergent near-neutrality." For different environmental conditions, our model predicts diverse vegetation types and trait mixtures, akin to observations. These results indicate that the outcomes of successional niche differentiation are richer than previously thought and potentially account for mixtures of traits and species observed in forests worldwide.

  7. Coexistence between wildlife and humans at fine spatial scales.

    PubMed

    Carter, Neil H; Shrestha, Binoj K; Karki, Jhamak B; Pradhan, Narendra Man Babu; Liu, Jianguo

    2012-09-18

    Many wildlife species face imminent extinction because of human impacts, and therefore, a prevailing belief is that some wildlife species, particularly large carnivores and ungulates, cannot coexist with people at fine spatial scales (i.e., cannot regularly use the exact same point locations). This belief provides rationale for various conservation programs, such as resettling human communities outside protected areas. However, quantitative information on the capacity and mechanisms for wildlife to coexist with humans at fine spatial scales is scarce. Such information is vital, because the world is becoming increasingly crowded. Here, we provide empirical information about the capacity and mechanisms for tigers (a globally endangered species) to coexist with humans at fine spatial scales inside and outside Nepal's Chitwan National Park, a flagship protected area for imperiled wildlife. Information obtained from field cameras in 2010 and 2011 indicated that human presence (i.e., people on foot and vehicles) was ubiquitous and abundant throughout the study site; however, tiger density was also high. Surprisingly, even at a fine spatial scale (i.e., camera locations), tigers spatially overlapped with people on foot and vehicles in both years. However, in both years, tigers offset their temporal activity patterns to be much less active during the day when human activity peaked. In addition to temporal displacement, tiger-human coexistence was likely enhanced by abundant tiger prey and low levels of tiger poaching. Incorporating fine-scale spatial and temporal activity patterns into conservation plans can help address a major global challenge-meeting human needs while sustaining wildlife.

  8. Multitrait successional forest dynamics enable diverse competitive coexistence

    PubMed Central

    Brännström, Åke; Westoby, Mark; Dieckmann, Ulf

    2017-01-01

    To explain diversity in forests, niche theory must show how multiple plant species coexist while competing for the same resources. Although successional processes are widespread in forests, theoretical work has suggested that differentiation in successional strategy allows only a few species stably to coexist, including only a single shade tolerant. However, this conclusion is based on current niche models, which encode a very simplified view of plant communities, suggesting that the potential for niche differentiation has remained unexplored. Here, we show how extending successional niche models to include features common to all vegetation—height-structured competition for light under a prevailing disturbance regime and two trait-mediated tradeoffs in plant function—enhances the diversity of species that can be maintained, including a diversity of shade tolerants. We identify two distinct axes of potential niche differentiation, corresponding to the traits leaf mass per unit leaf area and height at maturation. The first axis allows for coexistence of different shade tolerances and the second axis for coexistence among species with the same shade tolerance. Addition of this second axis leads to communities with a high diversity of shade tolerants. Niche differentiation along the second axis also generates regions of trait space wherein fitness is almost equalized, an outcome we term “evolutionarily emergent near-neutrality.” For different environmental conditions, our model predicts diverse vegetation types and trait mixtures, akin to observations. These results indicate that the outcomes of successional niche differentiation are richer than previously thought and potentially account for mixtures of traits and species observed in forests worldwide. PMID:28283658

  9. Parental harsh discipline in mainland China: prevalence, frequency, and coexistence.

    PubMed

    Wang, Meifang; Liu, Li

    2014-06-01

    The study examined the prevalence, frequency, and coexistence of psychological aggression (PA), corporal punishment (CP), and severe physical abuse (SPA) in mainland China. Using a sample of 2,518 father-mother dyads of 3-15-year-old children, the findings revealed that parental harsh discipline was prevalent in mainland China. The rates of harsh discipline in the current study fell in the middle of the ranges of rates found in other studies. Harsh discipline was most likely directed at boys or children aged 7 years and committed by mothers, young fathers, or high and low socioeconomic status (SES) parents. The prevalence of maternal and paternal PA and CP declined with the children's age. Maternal and paternal SPA first increased and then decreased with child age. The frequency of the three types of maternal and paternal harsh discipline fluctuated depending on the age of the children. In addition, approximately 50% of the mothers and fathers who reported using severe forms of disciplinary practices also engaged in less severe forms of harsh disciplinary practices against their children. SPA generally coexisted with CP and PA, and CP was usually accompanied by PA; however, PA was more likely to occur independently compared with CP and SPA. Moreover, maternal harsh discipline coexisted with paternal harsh discipline to some extent. The coexistence decreased with increasing severity of parental harsh discipline and differed according to child gender. These findings highlight the importance of studying these three types of parental harsh discipline simultaneously and intervening in harsh discipline by mothers and fathers within the same family.

  10. Sarcoidosis and primary biliary cirrhosis with co-existing myositis

    PubMed Central

    Hughes, P.; McGavin, C. R.

    1997-01-01

    In a small number of cases the co-existence of primary biliary cirrhosis and sarcoidosis is assumed from clinical serological and histological findings. A case of sarcoidosis is reported in which the M2 antibody, a highly specific marker for primary biliary cirrhosis, was detected. The patient also developed a severe myositis and a possible overlap syndrome is discussed. 




 PMID:9059489

  11. Gas-solid coexistence of the Lennard-Jones system

    NASA Astrophysics Data System (ADS)

    van der Hoef, Martin A.

    2002-09-01

    Recently, the absolute free energies of the Lennard-Jones system at solid-liquid and solid-gas coexistence were computed from Monte Carlo simulations [J. Chem. Phys. 116, 7145 (2002)]. In this note, we show that the values along the sublimation line are in good agreement with the results from an equation of state published earlier [J. Chem. Phys. 113, 8142 (2000)]. The present values for the thermodynamic properties along the sublimation line are the most accurate reported to date.

  12. Saddle point shapes of nuclei

    SciTech Connect

    Poenaru, D. N.; Plonski, I. H.; Greiner, W.

    2007-04-23

    Very general reflection asymmetrical saddle point nuclear shapes are obtained by solving an integro-differential equation without being necessary to specify a certain parametrization. This equation is derived as an Euler-Lagrange relationship associated to the variational problem of minimizing the potential energy with constraints (constant volume and given deformation parameter). The mass asymmetry in binary cold fission of Th and U isotopes is explained as the result of adding a phenomenological shell correction to the liquid drop model deformation energy. Applications to ternary fission are outlined.

  13. Coexistence of charge and ferromagnetic order in fcc Fe.

    PubMed

    Hsu, Pin-Jui; Kügel, Jens; Kemmer, Jeannette; Parisen Toldin, Francesco; Mauerer, Tobias; Vogt, Matthias; Assaad, Fakher; Bode, Matthias

    2016-03-14

    Phase coexistence phenomena have been intensively studied in strongly correlated materials where several ordered states simultaneously occur or compete. Material properties critically depend on external parameters and boundary conditions, where tiny changes result in qualitatively different ground states. However, up to date, phase coexistence phenomena have exclusively been reported for complex compounds composed of multiple elements. Here we show that charge- and magnetically ordered states coexist in double-layer Fe/Rh(001). Scanning tunnelling microscopy and spectroscopy measurements reveal periodic charge-order stripes below a temperature of 130 K. Close to liquid helium temperature, they are superimposed by ferromagnetic domains as observed by spin-polarized scanning tunnelling microscopy. Temperature-dependent measurements reveal a pronounced cross-talk between charge and spin order at the ferromagnetic ordering temperature about 70 K, which is successfully modelled within an effective Ginzburg-Landau ansatz including sixth-order terms. Our results show that subtle balance between structural modifications can lead to competing ordering phenomena.

  14. Digital Ecology: Coexistence and Domination among Interacting Networks

    NASA Astrophysics Data System (ADS)

    Kleineberg, Kaj-Kolja; Boguñá, Marián

    2015-05-01

    The overwhelming success of Web 2.0, within which online social networks are key actors, has induced a paradigm shift in the nature of human interactions. The user-driven character of Web 2.0 services has allowed researchers to quantify large-scale social patterns for the first time. However, the mechanisms that determine the fate of networks at the system level are still poorly understood. For instance, the simultaneous existence of multiple digital services naturally raises questions concerning which conditions these services can coexist under. Analogously to the case of population dynamics, the digital world forms a complex ecosystem of interacting networks. The fitness of each network depends on its capacity to attract and maintain users’ attention, which constitutes a limited resource. In this paper, we introduce an ecological theory of the digital world which exhibits stable coexistence of several networks as well as the dominance of an individual one, in contrast to the competitive exclusion principle. Interestingly, our theory also predicts that the most probable outcome is the coexistence of a moderate number of services, in agreement with empirical observations.

  15. Niche partitioning and species coexistence in a Neotropical felid assemblage

    NASA Astrophysics Data System (ADS)

    Di Bitetti, Mario S.; De Angelo, Carlos D.; Di Blanco, Yamil E.; Paviolo, Agustín

    2010-07-01

    Carnivores have been used as a model to understand the effects of competition in community structure. Behavioral mechanisms that facilitate species coexistence have been poorly explored and may explain the lack of community-wide morphological character displacement in some carnivore assemblages. We use the results of large-scale and intensive camera-trap surveys conducted in the Atlantic Forest of NE Argentina between 2003 and 2008 to describe the spatial patterns of detection and the daily pattern of records of the six wild cat species present in the region (jaguar Panthera onca, puma Puma concolor, ocelot Leopardus pardalis, jaguarundi Puma yagouaroundi, margay Leopardus wiedii, and oncilla Leopardus tigrinus). We use these patterns to generate hypotheses about behavioral differences that may facilitate species coexistence. The larger species were more frequently recorded in the better-protected areas, probably as a result of anthropogenic effects (poaching of cats and their prey). Competitive release from ocelots and jaguarundis may explain why the oncilla and the margay showed the opposite pattern. Morphologically similar species had the most contrasting activity patterns: the margay was exclusively nocturnal and the jaguarundi diurnal. The other species were cathemeral, but alternated their peaks of activity in relation to the relative order of their body weights. The contrasting temporal patterns observed and the ability of pumas and oncillas to adjust their activity patterns to local conditions may facilitate the coexistence of these cat species and explain the lack of character displacement in this assemblage.

  16. Coevolution of competing Callosobruchus species does not stabilize coexistence.

    PubMed

    Hausch, Stephen J; Fox, Jeremy W; Vamosi, Steven M

    2017-08-01

    Interspecific resource competition is expected to select for divergence in resource use, weakening interspecific relative to intraspecific competition, thus promoting stable coexistence. More broadly, because interspecific competition reduces fitness, any mechanism of interspecific competition should generate selection favoring traits that weaken interspecific competition. However, species also can adapt to competition by increasing their competitive ability, potentially destabilizing coexistence. We reared two species of bean beetles, the specialist Callosobruchus maculatus and the generalist C. chinensis, in allopatry and sympatry on a mixture of adzuki beans and lentils, and assayed mutual invasibility after four, eight, and twelve generations of evolution. Contrary to the expectation that coevolution of competitors will weaken interspecific competition, the rate of mutual invasibility did not differ between sympatry and allopatry. Rather, the invasion rate of C. chinensis, but not C. maculatus, increased with duration of evolution, as C. chinensis adapted to lentils without experiencing reduced adaptation to adzuki beans, and regardless of the presence or absence of C. maculatus. Our results highlight that evolutionary responses to interspecific competition promote stable coexistence only under specific conditions that can be difficult to produce in practice.

  17. Coexistence Analysis of Adjacent Long Term Evolution (LTE) Systems

    SciTech Connect

    Aulama, Mohannad M.; Olama, Mohammed M

    2013-01-01

    As the licensing and deployment of Long term evolution (LTE) systems are ramping up, the study of coexistence of LTE systems is an essential topic in civil and military applications. In this paper, we present a coexistence study of adjacent LTE systems aiming at evaluating the effect of inter-system interference on system capacity and performance as a function of some of the most common mitigation techniques: frequency guard band, base station (BS) antenna coupling loss, and user equipment (UE) antenna spacing. A system model is constructed for two collocated macro LTE networks. The developed model takes into consideration the RF propagation environment, power control scheme, and adjacent channel interference. Coexistence studies are performed for a different combination of time/frequency division duplex (TDD/FDD) systems under three different guard-bands of 0MHz, 5MHz, and 10MHz. Numerical results are presented to advice the minimum frequency guard band, BS coupling loss, and UE antenna isolation required for a healthy system operation.

  18. Acyl chain composition and coexisting fluid phases in lipid bilayers

    NASA Astrophysics Data System (ADS)

    Gu, Yongwen; Bradley, Miranda; Mitchell, Drake

    2011-10-01

    At room temperature phospholipid bilayers enriched in sphingolipids and cholesterol may form a solid phase as well as two coexisting fluid phases. These are the standard fluid phase, or the liquid-disordered phase, ld, and the liquid-ordered phase, lo, which is commonly associated with lipid rafts. Ternary mixtures of palmitoyl-oleoyl-phosphocholine (POPC; 16:0,18:1 PC), sphingomyelin (SPM), and cholesterol (Chol) form coexisting lo, ld and solid phases over a wide range of molar ratios. We are examining the ability of two fluorescent probes to detect these 2 phases: NBD linked to di-16:0 PE which partitions strongly into the lo phase and NBD linked to di-18:1 PE which partitions strongly into the ld phase. We are also examining the effect of the highly polyunsaturated phospholipid stearoyl-docosahexanoyl-phosphocholine (SDPC; 18:0, 22:6 PC) on the ternary phase diagram of POPC/SPM/Chol with particular focus on the functionally important lo/ld coexistence region. We report on the fluorescence lifetime and anisotropy decay dynamics of these two fluorescent probes.

  19. Tree-grass coexistence in the Everglades freshwater system

    NASA Astrophysics Data System (ADS)

    D'Odorico, P.; Carr, J. A.; Engel, V.

    2009-12-01

    The Everglades freshwater system exhibits a heterogeneous landscape with marshes punctuated by patches of woody vegetation (tree islands) that are typically more elevated than the surrounding marshes. Despite the diversity and spatial organization of vegetation within the tree and grass plant communities, the landscape of the Everglades exhibits the features of a two-phase system with a distinct contrast between tree islands and marshes: tree islands are more elevated, dominated by woody vegetation and relatively phosphorus rich, while marshes are grass dominated and phosphorus-poor. A parallel can be drawn between these tree-grass mosaics and the patchy vegetation typical of dryland ecosystems, particularly savannas. The coexistence of trees and grasses in patchy freshwater landscapes calls for an explanation of the underlying processes and of their susceptibility to changes in environmental conditions. We argue that the stable coexistence of sawgrass meadows and tree islands in the Everglades is the result of positive feedback mechanisms, which induce bistability in landscape dynamics. We develop a process-based zero-dimensional model to explain the coexistence of the alternative stable states of “marsh” and “tree island” in the Everglades’ freshwater landscape. This zero-dimensional model shows how alternative stable states may arise as an effect of the positive feedbacks.

  20. Digital Ecology: Coexistence and Domination among Interacting Networks.

    PubMed

    Kleineberg, Kaj-Kolja; Boguñá, Marián

    2015-05-19

    The overwhelming success of Web 2.0, within which online social networks are key actors, has induced a paradigm shift in the nature of human interactions. The user-driven character of Web 2.0 services has allowed researchers to quantify large-scale social patterns for the first time. However, the mechanisms that determine the fate of networks at the system level are still poorly understood. For instance, the simultaneous existence of multiple digital services naturally raises questions concerning which conditions these services can coexist under. Analogously to the case of population dynamics, the digital world forms a complex ecosystem of interacting networks. The fitness of each network depends on its capacity to attract and maintain users' attention, which constitutes a limited resource. In this paper, we introduce an ecological theory of the digital world which exhibits stable coexistence of several networks as well as the dominance of an individual one, in contrast to the competitive exclusion principle. Interestingly, our theory also predicts that the most probable outcome is the coexistence of a moderate number of services, in agreement with empirical observations.

  1. Digital Ecology: Coexistence and Domination among Interacting Networks

    PubMed Central

    Kleineberg, Kaj-Kolja; Boguñá, Marián

    2015-01-01

    The overwhelming success of Web 2.0, within which online social networks are key actors, has induced a paradigm shift in the nature of human interactions. The user-driven character of Web 2.0 services has allowed researchers to quantify large-scale social patterns for the first time. However, the mechanisms that determine the fate of networks at the system level are still poorly understood. For instance, the simultaneous existence of multiple digital services naturally raises questions concerning which conditions these services can coexist under. Analogously to the case of population dynamics, the digital world forms a complex ecosystem of interacting networks. The fitness of each network depends on its capacity to attract and maintain users’ attention, which constitutes a limited resource. In this paper, we introduce an ecological theory of the digital world which exhibits stable coexistence of several networks as well as the dominance of an individual one, in contrast to the competitive exclusion principle. Interestingly, our theory also predicts that the most probable outcome is the coexistence of a moderate number of services, in agreement with empirical observations. PMID:25988318

  2. Direct determination of liquid phase coexistence by Monte Carlo simulations.

    PubMed

    Zweistra, Henk J A; Besseling, N A M

    2006-07-01

    A formalism to determine coexistence points by means of Monte Carlo simulations is presented. The general idea of the method is to perform a simulation simultaneously in several unconnected boxes which can exchange particles. At equilibrium, most of the boxes will be occupied by a homogeneous phase. The compositions of these boxes yield coexisting points on the binodal. However, since the overall composition is fixed, at least one of the boxes will contain an interface. We show that this does not affect the results, provided that the interface has no net curvature. We coin the name "Helmholtz-ensemble method," because the method is related to the well-known Gibbs-ensemble method, but the volume of the boxes is constant. Since the box volumes are constant, we expect that this method will be particularly useful for lattice models. The accuracy of the Helmholtz-ensemble method is benchmarked against known coexistence curves of the three-dimensional Ising model with excellent results.

  3. Coexistence of intracranial epidermoid tumor and multiple cerebral aneurysms

    PubMed Central

    Yao, Pei-Sen; Lin, Zhang-Ya; Zheng, Shu-Fa; Lin, Yuan-Xiang; Yu, Liang-Hong; Jiang, Chang-Zhen; Kang, De-Zhi

    2017-01-01

    Abstract Rationale: There were a few case reports concerning epidermoid tumor coexisted with multiple cerebral aneurysms. Here, we present one case of coexistence of intracranial epidermoid tumor and multiple cerebral aneurysms and performed a literature review. Patient concerns: A 42 years old male patient was admitted to our institution with complaints of headache and dizziness. Interventions: The radiological examinations showed a hypointense lesion in the right parasellar and petrous apex region and an ipsilateral saccular aneurysm originated from the M2–M3 junction of the right middle cerebral artery (MCA) and a saccular aneurysm of the clinoid segment of right internal carotid artery (ICA). Interventions: The patients underwent a right frontotemporal approach for removal of the epidermoid tumor and clipping of the MCA aneurysm in one stage. The aneurysm located at the clinoid segment of ICA was invisible and untreated during operation. Outcomes: No postoperative complications were found in the patient. The patient's follow up after 5 years of surgical treatment was uneventful, and the untreated aneurysm remains stable. Lessons: The coexistence of intracranial epidermoid tumor and cerebral aneurysm is a rare event. The secondly inflammation in cerebral arterial wall may be responsible for the aneurysm formation. Surgical treatment of the intracranial epidermoid tumor and cerebral aneurysm repair may be an optimal scheme in one stage. PMID:28151901

  4. Mechanisms for stable coexistence in an insect community.

    PubMed

    Fan, Meng; Zhang, Bingbing; Li, Michael Yi

    2010-07-01

    In this paper, we formulate a three-species ecological community model consisting of two aphid species (Acyrthosiphon pisum and Megoura viciae) and a specialist parasitoid (Aphidius ervi) that attacks only one of the aphids (A pisum). The model incorporates both density-mediated and trait-mediated host-parasitoid interactions. Our analysis shows that the model possesses much richer and more realistic dynamics than earlier models. Our theoretical results reveal a new mechanism for stable coexistence in a three-species community in which any two species alone do not co-exist. More specifically, it is known that, when a predator is introduced into a community of two competing species, if the predator only predates on the strong competitor, it can allow the weak competitor to survive, but may drive the strong competitor to extinction through over-exploitation. We show that if the weak competitor interferes the predation on the strong competitor through trait-mediated indirect effects, then all three species can stably co-exist.

  5. Phase coexistence and competing interactions in complex oxides

    NASA Astrophysics Data System (ADS)

    Park, Soon Yong

    A significant progress in the materials physics research of the past decades, has been associated with the emerging paradigm of naturally or artificially fabricated heterogeneous structures/phases of complex materials with distinct physical phases, in which various physical degrees of freedoms are intricately coupled and charge carriers are strongly interacting. The heterogeneous structures/phases can be associated with various architectures and length-scales. For example, in the intrinsic multiferroics, magnetism and ferroelectricity are intricately mixed in atomic length-scales, but they coexist with much larger length scales such as micro-meters in the composite multiferroics. The recent investigation has revealed that the interplay between magnetism and ferroelectricity can be significant in magnetically-driven multiferroics where magnetic orders with broken inversion symmetry induce ferroelectric lattice distortions through exchange-striction. Herein, we focus on three systems with the coexistence of distinct physical phases: (1) an intrinsic multiferroic of a S = 1/2 chain cuprate, (2) a composite multiferroic fabricated by utilizing chemical/structural phase separation, and (3) a heterogeneous mixture where antiferromagnetic-insulating and high TC superconducting phases coexist. These novel systems reveal unprecedented physical properties and phenomena due to the presence of physical distinct phases in spatial proximity.

  6. Coexistence of charge and ferromagnetic order in fcc Fe

    PubMed Central

    Hsu, Pin-Jui; Kügel, Jens; Kemmer, Jeannette; Parisen Toldin, Francesco; Mauerer, Tobias; Vogt, Matthias; Assaad, Fakher; Bode, Matthias

    2016-01-01

    Phase coexistence phenomena have been intensively studied in strongly correlated materials where several ordered states simultaneously occur or compete. Material properties critically depend on external parameters and boundary conditions, where tiny changes result in qualitatively different ground states. However, up to date, phase coexistence phenomena have exclusively been reported for complex compounds composed of multiple elements. Here we show that charge- and magnetically ordered states coexist in double-layer Fe/Rh(001). Scanning tunnelling microscopy and spectroscopy measurements reveal periodic charge-order stripes below a temperature of 130 K. Close to liquid helium temperature, they are superimposed by ferromagnetic domains as observed by spin-polarized scanning tunnelling microscopy. Temperature-dependent measurements reveal a pronounced cross-talk between charge and spin order at the ferromagnetic ordering temperature about 70 K, which is successfully modelled within an effective Ginzburg–Landau ansatz including sixth-order terms. Our results show that subtle balance between structural modifications can lead to competing ordering phenomena. PMID:26971713

  7. Spatial coexistence of synchronized oscillation and death: A chimeralike state

    NASA Astrophysics Data System (ADS)

    Dutta, Partha Sharathi; Banerjee, Tanmoy

    2015-10-01

    We report an interesting spatiotemporal state, namely the chimeralike incongruous coexistence of synchronized oscillation and stable steady state (CSOD) in a network of nonlocally coupled oscillators. Unlike the chimera and chimera death state, in the CSOD state identical oscillators are self-organized into two coexisting spatially separated domains: In one domain neighboring oscillators show synchronized oscillation and in another domain the neighboring oscillators randomly populate either a synchronized oscillating state or a stable steady state (we call it a death state). We consider a realistic ecological network and show that the interplay of nonlocality and coupling strength results in two routes to the CSOD state: One is from a coexisting mixed state of amplitude chimera and death, and another one is from a globally synchronized state. We provide a qualitative explanation of the origin of this state. We further explore the importance of this study in ecology that gives insight into the relationship between spatial synchrony and global extinction of species. We believe this study will improve our understanding of chimera and chimeralike states.

  8. Periodic coexistence of four species competing for three essential resources.

    PubMed

    Li, Bingtuan; Smith, Hal L

    2003-08-01

    We show the existence of a periodic solution in which four species coexist in competition for three essential resources in the standard model of resource competition. By assuming that species i is limited by resource i for each i near the positive equilibrium, and that the matrix of contents of resources in species is a combination of cyclic matrix and a symmetric matrix, we obtain an asymptotically stable periodic solution of three species on three resources via Hopf bifurcation. A simple bifurcation argument is then employed which allows us to add a fourth species. In principle, the argument can be continued to obtain a periodic solution adding one new species at a time so long as asymptotic stability can be assured at each step. Numerical simulations are provided to illustrate our analytical results. The results of this paper suggest that competition can generate coexistence of species in the form of periodic cycles, and that the number of coexisting species can exceed the number of resources in a constant and homogeneous environment.

  9. The importance of niche differentiation for coexistence on large scales.

    PubMed

    Tang, Junfeng; Zhou, Shurong

    2011-03-21

    It is widely accepted that niche differentiation plays a key role in coexistence on relatively small scales. With regard to a large community scale, the recently propounded neutral theory suggests that species abundances are more influenced by history and chance than they are by interspecies competition. This inference is mainly based on the probability that competitive exclusion is largely slowed by recruitment limitation, which may be common in species rich communities. In this respect, a theoretical study conducted by Hurtt and Pacala (1995) for a niche differentiated community has been frequently cited to support neutral coexistence. In this paper, we focused on the effect of symmetric recruitment limitation on delaying species competitive exclusion caused by both symmetric and asymmetric competition in a large homogeneous habitat. By removing niche differentiation in space, we found that recruitment limitation could delay competitive exclusion to some extent, but the effect was rather limited compared to that predicted by Hurtt and Pacala's model for a niche differentiated community. Our results imply that niche differentiation may be important for species coexistence even on large scales and this has already been confirmed in some species rich communities. Copyright © 2010 Elsevier Ltd. All rights reserved.

  10. Shape of {sup 44}Ar: Onset of deformation in neutron-rich nuclei near {sup 48}Ca

    SciTech Connect

    Zielinska, M.; Goergen, A.; Clement, E.; Korten, W.; Dossat, C.; Ljungvall, J.; Obertelli, A.; Theisen, Ch.; Delaroche, J.-P.; Girod, M.; Buerger, A.; Catford, W.; Iwanicki, J.; Napiorkowski, P. J.; Srebrny, J.; Wrzosek, K.; Libert, J.; Rodriguez-Guzman, R.; Sletten, G.

    2009-07-15

    The development of deformation and shape coexistence in the vicinity of doubly magic {sup 48}Ca, related to the weakening of the N=28 shell closure, was addressed in a low-energy Coulomb excitation experiment using a radioactive {sup 44}Ar beam from the SPIRAL facility at GANIL. The 2{sub 1}{sup +} and 2{sub 2}{sup +} states in {sup 44}Ar were excited on {sup 208}Pb and {sup 109}Ag targets at two different beam energies. B(E2) values between all observed states and the spectroscopic quadrupole moment of the 2{sub 1}{sup +} state were extracted from the differential Coulomb excitation cross sections, indicating a prolate shape of the {sup 44}Ar nucleus and giving evidence of an onset of deformation already two protons and two neutrons away from doubly magic {sup 48}Ca. New Hartree-Fock-Bogoliubov based configuration mixing calculations have been performed with the Gogny D1S interaction for {sup 44}Ar and neighboring nuclei using two different approaches: the angular momentum projected generator coordinate method considering axial quadrupole deformations and a five-dimensional approach including the triaxial degree of freedom. The experimental values and new calculations are furthermore compared to shell-model calculations and to relativistic mean-field calculations. The new results give insight into the weakening of the N=28 shell closure and the development of deformation in this neutron-rich region of the nuclear chart.

  11. Nuclear Halos

    SciTech Connect

    Vogt, Erich

    2010-07-27

    We show that extreme nuclear halos are caused only by pairs of s-wave neutrons (or single s-wave neutrons) and that such states occur much more frequently in the periodic table than previously believed. Besides lingering long near zero neutron separation energy such extreme halos have very remarkable properties: they can contribute significantly to the nuclear density at more than twice the normal nuclear radius and their spreading width can be very narrow. The properties of these states are primarily determined by the ''thickness'' of the nuclear surface in the mean-free nuclear potential and thus their importance increases greatly as we approach the neutron drip line. We discuss what such extreme halos are, where they occur, what their properties are and some of their impact on nuclear observations.

  12. From Shape to Letters.

    ERIC Educational Resources Information Center

    Schiller, Hillel A.

    In order to make letter shape recognition an integral part of perception training, the use of the line in its two basic shapes is proposed. Letter shapes may seem exceedingly complex linear shapes to young minds. Thus instead of instruction in configuration, instruction involving transformational activities to manipulate and create the…

  13. Liquid disordered-liquid ordered phase coexistence in bicelles containing unsaturated lipids and cholesterol.

    PubMed

    Schmidt, Miranda L; Davis, James H

    2016-04-01

    Magnetically orienting bicelles are often made by combining the long chain phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with the short chain phospholipid 1,2-dicaproyl-sn-glycero-3-phosphocholine (DCPC) in buffer. These bicelles orient with their bilayer normals perpendicular to the external magnetic field. We have examined the phase behaviour of DMPC/DCPC bicelles and the effects of cholesterol and the unsaturated phospholipid 1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine (DPoPC) as a function of temperature using static solid state (2)H nuclear magnetic resonance spectroscopy. As expected, cholesterol has an ordering effect on the long phospholipid chains and this is reflected in the phase behaviour of the bicelle mixtures. Liquid disordered-liquid ordered, fluid-fluid phase coexistence is observed in DMPC/cholesterol/DCPC bicelles with cholesterol mole fractions of 0.13 and higher. DPoPC/DMPC/cholesterol/DCPC bicelles also exhibit two fluid phase coexistence over a broad range of temperatures and compositions. Bicelles can provide a useful medium in which to study membrane bound peptides and proteins. The orientation parallel to the magnetic field is favourable for studying membrane peptides/proteins because information about the orientation of relevant molecular bonds or internuclear vectors can be obtained directly from the resulting (2)H spectra. Lanthanide ions can be used to flip the bicelles to have their bilayer normals parallel to the external magnetic field. Yb(3+) was used to flip the DPoPC/DMPC/cholesterol/DCPC bicelles while Eu(3+) was found to be ineffective at flipping bicelles containing cholesterol in the present work.

  14. Nuclear astrophysics

    SciTech Connect

    Haxton, W.C.

    1992-01-01

    The problem of core-collapse supernovae is used to illustrate the many connections between nuclear astrophysics and the problems nuclear physicists study in terrestrial laboratories. Efforts to better understand the collapse and mantle ejection are also motivated by a variety of interdisciplinary issues in nuclear, particle, and astrophysics, including galactic chemical evolution, neutrino masses and mixing, and stellar cooling by the emission of new particles. The current status of theory and observations is summarized.

  15. Nuclear astrophysics

    SciTech Connect

    Haxton, W.C.

    1992-12-31

    The problem of core-collapse supernovae is used to illustrate the many connections between nuclear astrophysics and the problems nuclear physicists study in terrestrial laboratories. Efforts to better understand the collapse and mantle ejection are also motivated by a variety of interdisciplinary issues in nuclear, particle, and astrophysics, including galactic chemical evolution, neutrino masses and mixing, and stellar cooling by the emission of new particles. The current status of theory and observations is summarized.

  16. Nuclear Autonomy in Multinucleate Fungi

    PubMed Central

    Roberts, Samantha E.; Gladfelter, Amy S.

    2015-01-01

    Within many fungal syncytia, nuclei behave independently despite sharing a common cytoplasm. Creation of independent nuclear zones of control in one cell is paradoxical considering random protein synthesis sites, predicted rapid diffusion rates, and well-mixed cytosol. In studying the surprising fungal nuclear autonomy, new principles of cellular organization are emerging. We discuss the current understanding of nuclear autonomy, focusing on asynchronous cell cycle progression where most work has been directed. Mechanisms underlying nuclear autonomy are diverse including mRNA localization, ploidy variability, and nuclear spacing control. With the challenges fungal syncytia face due to cytoplasmic size and shape, they serve as powerful models for uncovering new subcellular organization modes, variability sources among isogenic uninucleate cells, and the evolution of multicellularity. PMID:26379197

  17. Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Denschlag, J. O.

    This chapter first gives a survey on the history of the discovery of nuclear fission. It briefly presents the liquid-drop and shell models and their application to the fission process. The most important quantities accessible to experimental determination such as mass yields, nuclear charge distribution, prompt neutron emission, kinetic energy distribution, ternary fragment yields, angular distributions, and properties of fission isomers are presented as well as the instrumentation and techniques used for their measurement. The contribution concentrates on the fundamental aspects of nuclear fission. The practical aspects of nuclear fission are discussed in http://dx.doi.org/10.1007/978-1-4419-0720-2_57 of Vol. 6.

  18. Nuclear Safety

    SciTech Connect

    Silver, E G

    1989-01-01

    This document is a review journal that covers significant developments in the field of nuclear safety. Its scope includes the analysis and control of hazards associated with nuclear energy, operations involving fissionable materials, and the products of nuclear fission and their effects on the environment. Primary emphasis is on safety in reactor design, construction, and operation; however, the safety aspects of the entire fuel cycle, including fuel fabrication, spent-fuel processing, nuclear waste disposal, handling of radioisotopes, and environmental effects of these operations, are also treated.

  19. Shape memory polymers

    DOEpatents

    Wilson, Thomas S.; Bearinger, Jane P.

    2017-08-29

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  20. Shape memory polymers

    DOEpatents

    Wilson, Thomas S.; Bearinger, Jane P.

    2015-06-09

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  1. Coexistent Regime of H-mode with a Dense & Cold Divorter plasma in JFT-2M Closed Divertor

    NASA Astrophysics Data System (ADS)

    Sengoku, Seio; JFT-2m Group

    1996-11-01

    A possibility of stable coexistence of an H-mode with a dense & cold divertor plasma had been demonstrated using a strong gas puffing in divertor chamber at the lower density limit for the H-mode transition ( 2x10^19m-3: the regime of no spontaneous dense & cold state) by modifying the divertor shape of JFT-2M to a closed configuration.footnote S. Sengoku et al., Bull. Amer. Phys. Soc. 40, 1675 (1995) A build up of neutral pressure occurs only in the divertor chamber without degrading the H-factor, and the divertor plasma results in a dense & cold state (n_e=1.3 2.5x 10^19m-3, T_e=4 15eV). In order to improve baffling effect and to extend operational regime of the coexistence, the divertor baffle plates of JFT-2M had been modified from relatively wide baffle-opening to more closed one. Studies on fueling and exhaustion, particle control, neutral buildup scaling and SOL plasma behaviors are being carried out with the modified divertor shape.

  2. Co-existence of porokeratosis variants concurrent with Bowen's disease: two rare cases report.

    PubMed

    Korviriyakamol, Tarinee; Kattipathananpong, Pinnaree; Chunhasewee, Chakkrapong; Wessagowit, Vesarat; Kootiratrakarn, Tanawatt

    2014-03-01

    Coexisting variants of porokeratosis rarely occurs. Disseminated superficial porokeratosis (DSP) is characterized by multiple uniform small annular papules distributed all over body. DSP commonly coexist with linear porokeratosis (LP), but it is uncommon for DSP to coexist with porokeratosis of Mibelli (PM). PM presents with central atrophic erythematous plaques and thread-like elevated border. It occurs mainly on extremities. Although malignant transformation can be found in the porokeratosis, there is still no report case of coexisting variants of porokeratosis concurrent with Bowen's disease. The clinical and histopathologic finding of rare coexisting variants of porokeratosis (PM and DSP) concurrent with squamous dysplasia is described.

  3. Dynamics of microbial growth and coexistence on variably saturated rough surfaces.

    PubMed

    Long, Tao; Or, Dani

    2009-08-01

    The high degree of microbial diversity found in soils is attributed to the highly heterogeneous pore space and the dynamic aqueous microenvironments. Previous studies have shown that spatial and temporal variations in aqueous diffusion pathways play an important role in shaping microbial habitats and biological activity in unsaturated porous media. A new modeling framework was developed for the quantitative description of diffusion-dominated microbial interactions focusing on competitive growth of two microbial species inhabiting partially saturated rough surfaces. Surface heterogeneity was represented by patches with different porosities and water retention properties, yielding heterogeneous distribution of water contents that varies with changes in relative humidity or soil matric potential. Nutrient diffusion and microbial growth on the variably hydrated and heterogeneous surface was modeled using a hybrid method that combines a reaction diffusion method for nutrient field with individual based model for microbial growth and expansion. The model elucidated the effects of hydration dynamics and heterogeneity on nutrient fluxes and mobility affecting microbial population growth, expansion, and coexistence at the microscale. In contrast with single species dominance under wet conditions, results demonstrated prolonged coexistence of two competing species under drier conditions where nutrient diffusion and microbial movement were both limited. The uneven distribution of resources and diffusion pathways in heterogeneous surfaces highlighted the importance of position in the landscape for survival that may compensate for competitive disadvantages conferred by physiological traits. Increased motility was beneficial for expansion and survival. Temporal variations in hydration conditions resulted in fluctuations in microbial growth rate and population size. Population growth dynamics of the dominant species under wet-dry cycles were similar to growth under average value

  4. Regulating coexistence of GM and non-GM crops without jeopardizing economic incentives.

    PubMed

    Demont, Matty; Devos, Yann

    2008-07-01

    The ongoing debate about the coexistence of genetically modified (GM) and non-GM crops in the European Union (EU) mainly focuses on preventive measures needed to keep the adventitious presence of GM material in non-GM products below established tolerance thresholds, as well as on issues covering questions of liability and the duty to redress the incurred economic harm once adventitious mixing in non-GM products has occurred. By contrast, the interplay between the economic incentives and costs of coexistence has attracted little attention. The current overemphasis on the technical aspects and cost of coexistence over its economic incentives might lead EU policy-makers to adopt too stringent and rigid regulations on coexistence. Therefore, we argue for flexible coexistence regulations that explicitly take into account the economic incentives for coexistence. Our arguments provide a timely and important framework for EU policy-makers, who are currently struggling to implement coherent coexistence regulations in all member states.

  5. High-spin nuclear spectroscopy

    SciTech Connect

    Diamond, R.M.

    1986-07-01

    High-spin spectroscopy is the study of the changes in nuclear structure, properties, and behavior with increasing angular momentum. It involves the complex interplay between collective and single-particle motion, between shape and deformation changes, particle alignments, and changes in the pairing correlations. A review of progress in theory, experimentation, and instrumentation in this field is given. (DWL)

  6. Nuclear safety

    NASA Technical Reports Server (NTRS)

    Buden, D.

    1991-01-01

    Topics dealing with nuclear safety are addressed which include the following: general safety requirements; safety design requirements; terrestrial safety; SP-100 Flight System key safety requirements; potential mission accidents and hazards; key safety features; ground operations; launch operations; flight operations; disposal; safety concerns; licensing; the nuclear engine for rocket vehicle application (NERVA) design philosophy; the NERVA flight safety program; and the NERVA safety plan.

  7. Nuclear privatization

    SciTech Connect

    Jeffs, E.

    1995-11-01

    The United Kingdom government announced in May 1995 plans to privatize the country`s two nuclear generating companies, Nuclear Electric and Scottish Nuclear. Under the plan, the two companies will become operating divisions of a unified holding company, to be called British Electric, with headquarters in Scotland. Britain`s nuclear plants were left out of the initial privatization in 1989 because the government believed the financial community would be unwilling to accept the open-ended liability of decommissioning the original nine stations based on the Magnox gas-cooled reactor. Six years later, the government has found a way around this by retaining these power stations in state ownership, leaving the new nuclear company with the eight Advanced Gas-cooled Reactor (AGR) stations and the recently completed Sizewell B PWR stations. The operating Magnox stations are to be transferred to BNFL, which operates two Magnox stations of their own at Calder Hall and Chapelcross.

  8. Nuclear materials

    SciTech Connect

    Not Available

    1992-08-01

    The Department of Energy (DOE) processes plutonium for use in nuclear weapons. This fact sheet responds to your September 6, 1991, request, that we describe the methods and facilities for DOE's plutonium processing. Plutonium, which is used to make nuclear weapons, does not exist in nature and has to be produced. However, DOE no longer produces plutonium for use in nuclear weapons. Instead, DOE processes and recycles the plutonium from retired nuclear weapons and the plutonium that remains as scrap or residue from plutonium processing. This paper reports that DOE recovers plutonium through two basic processes-aqueous and pyrochemical-at four processing sites-Rocky Flats, Savannah River, Hanford, and Los Alamos. However, because of environmental and safety concerns and reductions in nuclear weapons, DOE has closed or may close most of the processing facilities. Only Los Alamos' processing facilities are currently operating.

  9. Co-existence of Functionally Different Vesicular Neurotransmitter Transporters

    PubMed Central

    Münster-Wandowski, Agnieszka; Zander, Johannes-Friedrich; Richter, Karin; Ahnert-Hilger, Gudrun

    2016-01-01

    The vesicular transmitter transporters VGLUT, VGAT, VMAT2 and VAChT, define phenotype and physiological properties of neuronal subtypes. VGLUTs concentrate the excitatory amino acid glutamate, VGAT the inhibitory amino acid GABA, VMAT2 monoamines, and VAChT acetylcholine (ACh) into synaptic vesicle (SV). Following membrane depolarization SV release their content into the synaptic cleft. A strict segregation of vesicular transporters is mandatory for the precise functioning of synaptic communication and of neuronal circuits. In the last years, evidence accumulates that subsets of neurons express more than one of these transporters leading to synaptic co-release of different and functionally opposing transmitters and modulation of synaptic plasticity. Synaptic co-existence of transporters may change during pathological scenarios in order to ameliorate misbalances in neuronal activity. In addition, evidence increases that transporters also co-exist on the same vesicle providing another layer of regulation. Generally, vesicular transmitter loading relies on an electrochemical gradient ΔμH+ driven by the proton ATPase rendering the lumen of the vesicle with respect to the cytosol positive (Δψ) and acidic (ΔpH). While the activity of VGLUT mainly depends on the Δψ component, VMAT, VGAT and VAChT work best at a high ΔpH. Thus, a vesicular synergy of transporters depending on the combination may increase or decrease the filling of SV with the principal transmitter. We provide an overview on synaptic co-existence of vesicular transmitter transporters including changes in the excitatory/inhibitory balance under pathological conditions. Additionally, we discuss functional aspects of vesicular synergy of transmitter transporters. PMID:26909036

  10. Plant-mediated resource partitioning by coexisting parasitoids.

    PubMed

    Xi, Xinqiang; Yang, Yangheshan; Yang, Yonghua; Segoli, Michal; Sun, Shucun

    2017-03-29

    Although it has been frequently suggested that resource partitioning of species coexisting at the same trophic level can be mediated by interactions with species at non-adjacent trophic levels, empirical evidence supporting this claim is scarce. Here we demonstrate that plants may mediate resource partitioning for two parasitoids that share the same herbivorous host. The tephritid fly Tephritis femoralis is the primary pre-dispersal seed predator of two Asteraceae species, Saussurea nigrescens and Anaphalis flavescens, both of which dominate the plant community in the alpine meadows of the Tibetan Plateau. Field surveys and molecular barcoding analyses showed that the identity of the fly's main predator depended on the plant in which the fly developed. Tephritid flies that developed in S. nigrescens were preyed upon mainly by the parasitoid wasp Pteromalus albipennis, while the parasitoid Mesopolobus sp. was the main predator of flies that developed in A. flavescens. Microcosm experiments revealed that P. albipennis could not exploit the host flies within the capitula of A. flavescens due to food limitation (capitula are too small), while Mesopolobus sp. could not exploit the host flies within the capitula of S. nigrescens due to its inability to reach the host with its ovipositor (capitula are too large). Such bottom-up control of plant species traits may facilitate the coexistence of parasitoid wasps sharing a common host in this system. We suggest that interactions between non-adjacent trophic levels may potentially promote species coexistence and diversity in biological communities. This article is protected by copyright. All rights reserved.

  11. Co-existence of Functionally Different Vesicular Neurotransmitter Transporters.

    PubMed

    Münster-Wandowski, Agnieszka; Zander, Johannes-Friedrich; Richter, Karin; Ahnert-Hilger, Gudrun

    2016-01-01

    The vesicular transmitter transporters VGLUT, VGAT, VMAT2 and VAChT, define phenotype and physiological properties of neuronal subtypes. VGLUTs concentrate the excitatory amino acid glutamate, VGAT the inhibitory amino acid GABA, VMAT2 monoamines, and VAChT acetylcholine (ACh) into synaptic vesicle (SV). Following membrane depolarization SV release their content into the synaptic cleft. A strict segregation of vesicular transporters is mandatory for the precise functioning of synaptic communication and of neuronal circuits. In the last years, evidence accumulates that subsets of neurons express more than one of these transporters leading to synaptic co-release of different and functionally opposing transmitters and modulation of synaptic plasticity. Synaptic co-existence of transporters may change during pathological scenarios in order to ameliorate misbalances in neuronal activity. In addition, evidence increases that transporters also co-exist on the same vesicle providing another layer of regulation. Generally, vesicular transmitter loading relies on an electrochemical gradient ΔμH(+) driven by the proton ATPase rendering the lumen of the vesicle with respect to the cytosol positive (Δψ) and acidic (ΔpH). While the activity of VGLUT mainly depends on the Δψ component, VMAT, VGAT and VAChT work best at a high ΔpH. Thus, a vesicular synergy of transporters depending on the combination may increase or decrease the filling of SV with the principal transmitter. We provide an overview on synaptic co-existence of vesicular transmitter transporters including changes in the excitatory/inhibitory balance under pathological conditions. Additionally, we discuss functional aspects of vesicular synergy of transmitter transporters.

  12. Coexisting attractors in compressible Rayleigh-Bénard flow

    NASA Astrophysics Data System (ADS)

    Castillo, V. M.; Hoover, Wm. G.; Hoover, C. G.

    1997-05-01

    We demonstrate that precise solutions of the convective flow equations for a compressible conducting viscous fluid can give degenerate stationary states. That is, two or more completely different stable flows can result for fixed stationary boundary conditions. We characterize these complex flows with finite-difference, smooth-particle methods, and high-order implicit methods. The fluids treated here are viscous conducting gases, enclosed by thermal boundaries in a gravitational field-the ``Rayleigh-Bénard problem.'' Degenerate solutions occur in both two- and three-dimensional simulations. This coexistence of solutions is a macroscopic manifestation of the strange attractors seen in atomistic systems far from equilibrium.

  13. Ghost free systems with coexisting bosons and fermions

    NASA Astrophysics Data System (ADS)

    Kimura, Rampei; Sakakihara, Yuki; Yamaguchi, Masahide

    2017-08-01

    We study the coexistence system of both bosonic and fermionic degrees of freedom. Even if a Lagrangian does not include higher derivatives, fermionic ghosts exist. For a Lagrangian with up to first derivatives, we find the fermionic ghost free condition in Hamiltonian analysis, which is found to be the same as requiring that the equations of motion of fermions be first order in Lagrangian formulation. When fermionic degrees of freedom are present, the uniqueness of time evolution is not guaranteed a priori because of the Grassmann property. We confirm that the additional condition, which is introduced to close Hamiltonian analysis, also ensures the uniqueness of the time evolution of the system.

  14. Co-Existence of Multicentric Castleman's Disease and Kaposi's Sarcoma

    PubMed Central

    Yaghoobi, Reza; Pazyar, Nader; Tavakoli, Sadigheh

    2015-01-01

    Castleman's disease (CD) or giant lymph node hyperplasia is a rare disorder that can be unicentric or multicentric. Multicentric Castleman's disease (MCD) is manifested by generalized lymphadenopathy, hepatosplenomegaly, polyclonal hypergammaglobulinemia, hematological abnormality, and constitutional symptoms. Human herpesvirus 8 (HHV-8) infection is present in nearly 100% MCD associated with HIV-1 infection, but in about 50% of cases of HIV negative. Herein, we report a 77-year-old man with systemic involvement and skin lesions on the anterior aspect of both legs in the previous site of saphenous vein angioplasty. Co-existence of MCD with Kaposi's sarcoma (KS) led us to present this rare case. PMID:26120185

  15. Effect of hyperons on phase coexistence in strange matter

    NASA Astrophysics Data System (ADS)

    Das, P.; Mallik, S.; Chaudhuri, G.

    2017-01-01

    The study of the liquid gas phase transition in the fragmentation of nuclei in heavy ion collisions has been extended to the strangeness sector using the statistical model for multifragmentation. Helmholtz's free energy, specific heat, and a few other thermodynamic observables have been analyzed in order to examine the occurrence of phase transition in the strange matter. The bimodal behavior of the largest cluster formed in fragmentation also strongly indicates a coexistence of both the phases. The presence of hyperons strengthens the signals and also shifts the transition temperature to lower values.

  16. Coexistence of three specialist aphids on common milkweed, Asclepias syriaca.

    PubMed

    Smith, R A; Mooney, K A; Agrawal, A A

    2008-08-01

    Coexistence of host-specific herbivores on plants is believed to be governed by interspecific interactions, but few empirical studies have systematically unraveled these dynamics. We investigated the role of several factors in promoting coexistence among the aphids Aphis nerii, Aphis asclepiadis, and Myzocallis asclepiadis that all specialize on common milkweed (Asclepias syriaca). Competitive exclusion is thought to occur when interspecific competition is stronger than intraspecific competition. Consequently, we investigated whether predators, mutualists, or resource quality affected the strength of intra- vs. interspecific competition among aphids in factorial manipulations of competition with exposure to predation, ants, and variable plant genotypes in three separate experiments. In the predation x competition experiment, predators reduced aphid per capita growth by 66%, but the strength of intra- and interspecific competition did not depend on predators. In the ants x competition experiment, ants reduced per capita growth of A. nerii and M. asclepiadis (neither of which were mutualists with ants) by approximately one-half. In so doing, ants ameliorated the negative effects of these competitors on ant-tended A. asclepiadis by two-thirds, representing a novel benefit of ant-aphid mutualism. Nevertheless, ants alone did not explain the persistence of competitively inferior A. asclepiadis as, even in the presence of ants, interspecific competition remained stronger than intraspecific competition. In the plant genotype x competition experiment, both A. asclepiadis and M. asclepiadis were competitively inferior to A. nerii, with the strength of interspecific competition exceeding that of intraspecific competition by 83% and 23%, respectively. Yet these effects differed among milkweed genotypes, and there were one or more plant genotypes for each aphid species where coexistence was predicted. A synthesis of our results shows that predators play little or no role in

  17. Evidence for coexistence of Rashba and Dresselhaus effect on semiconductor

    NASA Astrophysics Data System (ADS)

    Jung, Wonsig; Jo, S. H.; Kim, B. Y.; Leandersson, M.; Thiagarajan, B.; Hong, J. S.; Shim, J. H.; Kim, Changyoung

    2014-03-01

    We have performed preliminary circular dichroism angle-resolved photoemission spectroscopy (ARPES) experiments on InSb. Our results show very strong circular dichroism (CD) signal, indicating probable existence of orbital angular momentum (OAM). Non-zero OAM in zincblend semiconductor can appear when there is an inversion symmetry breaking (IBS) in the bulk and on the surface. We find that the dichroism has momentum and band dependence. The CD modulations can be the evidence for coexistence of Rashba and Dresselhaus effect on semiconductor.

  18. Electrical signaling and photosynthesis: can they co-exist together?

    PubMed

    Pavlovič, Andrej; Mancuso, Stefano

    2011-06-01

    Mechanical irritation of trigger hairs and subsequent generation of action potentials have significant impact on photosynthesis and respiration in carnivorous Venus flytrap (Dionaea muscipula). Action potential-mediated inhibition of photosynthesis and stimulation of respiration is confined only to the trap and was not recorded in adjacent photosynthetic lamina. We showed that the main primary target of electrical signals on assimilation is in the dark enzymatic reaction of photosynthesis. Without doubt, the electrical signaling is costly, and the possible co-existence of such type of signals and photosynthesis in plant cell is discussed.

  19. Myasthenia gravis and thymoma coexisting with myotonic dystrophy type 1.

    PubMed

    Ekmekci, Ozgul; Karasoy, Hatice; Bademkiran, Fikret; Akkus, Dilek Evyapan; Yuceyar, Nur

    2014-01-01

    We describe a 34-year old man presenting with subacute generalized myasthenic symptoms. His clinical features and laboratory investigations demonstrated both myasthenia gravis and myotonic dystrophy type 1. The computerized tomography of chest revealed anterior mediastinal mass. The lymphocyte-rich thymoma was removed surgically and he received radiotherapy. Recent observations suggested that the patients with myotonic dystrophy may have an increased risk of benign and malignant tumours but its coexistence with thymoma is very rare. The risk of thymoma associated with myotonic dystrophy is unknown.

  20. Coal and climate regulations can co-exist

    SciTech Connect

    Rogers, J.

    2006-07-15

    Jim Rogers, president and chief executive officer of Duke Energy Corporation, examines how coal and climate change regulations can co-exist. He addresses the need for economically sound choices for future energy needs, which is complicated by what he refers to as 'the elephant in the room'climate change. He observes that new CO{sub 2} regulations would increase the USA's cost of generating electricity over time and result in higher prices for customers, and he advocates that a gradual, economy-wide, market-based U.S. climate policy is the best option. 1 ref., 1 fig.

  1. Coexistence of superconductivity and ferromagnetism in ferromagnetic metals.

    PubMed

    Karchev, N I; Blagoev, K B; Bedell, K S; Littlewood, P B

    2001-01-29

    We address the question of coexistence of superconductivity and ferromagnetism. Using a field theoretical approach we study a one-fermion effective model of a ferromagnetic superconductor in which the quasiparticles responsible for the ferromagnetism form the Cooper pairs as well. For the first time we solve self-consistently the mean-field equations for the superconducting gap and the spontaneous magnetization. We discuss the physical features which are different in this model and the standard BCS model and consider their experimental consequences.

  2. Unusual nature of ferromagnetism coexisting with superconductivity in UGe2.

    PubMed

    Nishioka, T; Motoyama, G; Nakamura, S; Kadoya, H; Sato, N K

    2002-06-10

    We report the discovery of a jump in the magnetization of a macroscopic single crystalline sample of UGe2 that shows coexistence of ferromagnetism and superconductivity. In particular, we observe that the jump occurs at regular intervals of field and only at very low temperatures. This novel feature implies that the magnetic field induces a sudden change of the direction of the magnetization between two equivalent easy axes of magnetization even in a macroscopic sample. We ascribe it to a field-tuned resonant tunneling between quantum spin states, and we propose that the size of a magnetic domain is smaller than a superconducting coherence length.

  3. Takotsubo Cardiomyopathy Coexisting with Acute Pericarditis and Myocardial Bridge

    PubMed Central

    Sezavar, Seyed Hashem; Riahi Beni, Hassan; Ghanavati, Reza; Hajahmadi, Marjan

    2016-01-01

    Takotsubo cardiomyopathy (TCM) is a stress-induced cardiomyopathy that occurs primarily in postmenopausal women. It mimics clinical picture of acute coronary syndrome with nonobstructive coronary arteries and a characteristic transient left (or bi-) ventricular apical ballooning at angiography. The exact pathogenesis of TCM is not well recognized. Hereby we present an unusual case of TCM that presents with signs and symptoms of acute pericarditis and was also found to have a coexisting coronary muscle bridge on coronary angiography. We discuss the impact of these associations in better understanding of the pathogenesis of TCM. PMID:27437150

  4. Analysis of Nuclear Quantum Phase Transitions

    SciTech Connect

    Li, Z. P.; Meng, J.; Niksic, T.; Vretenar, D.; Lalazissis, G. A.; Ring, P.

    2009-08-26

    A microscopic analysis, based on nuclear energy density functionals, is presented for shape phase transitions in Nd isotopes. Low-lying excitation spectra and transition probabilities are calculated starting from a five-dimensional Hamiltonian, with parameters determined by constrained relativistic mean-field calculations for triaxial shapes. The results reproduce available data, and show that there is an abrupt change of structure at N = 90, that corresponds to a first-order quantum phase transition between spherical and axially deformed shapes.

  5. Hot magnetized nuclear matter: Thermodynamic and saturation properties

    NASA Astrophysics Data System (ADS)

    Rezaei, Z.; Bordbar, G. H.

    2017-03-01

    We have used a realistic nuclear potential, AV_{18}, and a many-body technique, the lowest-order constraint variational (LOCV) approach, to calculate the properties of hot magnetized nuclear matter. By investigating the free energy, spin polarization parameter, and symmetry energy, we have studied the temperature and magnetic field dependence of the saturation properties of magnetized nuclear matter. In addition, we have calculated the equation of state of magnetized nuclear matter at different temperatures and magnetic fields. It was found that the flashing temperature of nuclear matter decreases by increasing the magnetic field. In addition, we have studied the effect of the magnetic field on liquid gas phase transition of nuclear matter. The liquid gas coexistence curves, the order parameter of the liquid gas phase transition, and the properties of critical point at different magnetic fields have been calculated.

  6. Nuclear overlap functions

    SciTech Connect

    Eskola, K.J.; Vogt, R.; Wang, X.N.

    1995-07-01

    A three parameter Wood-Saxon shape is used to describe the nuclear density distribution, which R{sub A} is the nuclear radius, {approx} is the surface thickness, and {omega} allows for central irregularities. The electron scattering data is used where available for R{sub A}, z, and {omega}. When data is unavailable, the parameters {omega} = O, z = 0.54 fm and R{sub A} = 1.19 A{sup 1/3} - 1.61 A{sup -1/3} fm are used. The central density {rho}{sub 0} is found from the normalization {infinity} d{sup 3}r{rho}{sub A}(r) = A.

  7. Self-erecting shapes

    DOEpatents

    Reading, Matthew W.

    2017-07-04

    Technologies for making self-erecting structures are described herein. An exemplary self-erecting structure comprises a plurality of shape-memory members that connect two or more hub components. When forces are applied to the self-erecting structure, the shape-memory members can deform, and when the forces are removed the shape-memory members can return to their original pre-deformation shape, allowing the self-erecting structure to return to its own original shape under its own power. A shape of the self-erecting structure depends on a spatial orientation of the hub components, and a relative orientation of the shape-memory members, which in turn depends on an orientation of joining of the shape-memory members with the hub components.

  8. Shaped Recess Flow Control

    NASA Technical Reports Server (NTRS)

    Shyam, Vikram (Inventor); Poinsatte, Philip (Inventor); Thurman, Douglas (Inventor)

    2017-01-01

    One or more embodiments of techniques or systems for shaped recess flow control are provided herein. A shaped recess or cavity can be formed on a surface associated with fluid flow. The shaped recess can be configured to create or induce fluid effects, temperature effects, or shedding effects that interact with a free stream or other structures. The shaped recess can be formed at an angle to a free stream flow and may be substantially "V" shaped. The shaped recess can be coupled with a cooling channel, for example. The shaped recess can be upstream or downstream from a cooling channel and aligned in a variety of manners. Due to the fluid effects, shedding effects, and temperature effects created by a shaped recess, lift-off or separation of cooling jets of cooling channels can be mitigated, thereby enhancing film cooling effectiveness.

  9. Nuclear reprogramming.

    PubMed

    Halley-Stott, Richard P; Pasque, Vincent; Gurdon, J B

    2013-06-01

    There is currently particular interest in the field of nuclear reprogramming, a process by which the identity of specialised cells may be changed, typically to an embryonic-like state. Reprogramming procedures provide insight into many mechanisms of fundamental cell biology and have several promising applications, most notably in healthcare through the development of human disease models and patient-specific tissue-replacement therapies. Here, we introduce the field of nuclear reprogramming and briefly discuss six of the procedures by which reprogramming may be experimentally performed: nuclear transfer to eggs or oocytes, cell fusion, extract treatment, direct reprogramming to pluripotency and transdifferentiation.

  10. The Hue of Shapes

    ERIC Educational Resources Information Center

    Albertazzi, Liliana; Da Pos, Osvaldo; Canal, Luisa; Micciolo, Rocco; Malfatti, Michela; Vescovi, Massimo

    2013-01-01

    This article presents an experimental study on the naturally biased association between shape and color. For each basic geometric shape studied, participants were asked to indicate the color perceived as most closely related to it, choosing from the Natural Color System Hue Circle. Results show that the choices of color for each shape were not…

  11. The Hue of Shapes

    ERIC Educational Resources Information Center

    Albertazzi, Liliana; Da Pos, Osvaldo; Canal, Luisa; Micciolo, Rocco; Malfatti, Michela; Vescovi, Massimo

    2013-01-01

    This article presents an experimental study on the naturally biased association between shape and color. For each basic geometric shape studied, participants were asked to indicate the color perceived as most closely related to it, choosing from the Natural Color System Hue Circle. Results show that the choices of color for each shape were not…

  12. Coexistence of osteopoikilosis with seronegative spondyloarthritis and spinal stenosis

    PubMed Central

    Demir, Saliha Eroglu; Özaras, Nihal; Poyraz, Emine; Toprak, Hüseyin; Güler, Mustafa

    2015-01-01

    [Purpose] Osteopoikilosis is a rare hereditary bone disease that is usually asymptomatic. It is generally diagnosed incidentally on plain radiography. The coexistence of osteopoikilosis with seronegative spondyloarthritis or spinal stenosis is rarely reported. Here, we report the case of a 27-year-old male patient with osteopoikilosis, seronegative spondyloarthritis, and spinal stenosis. [Subject] A 27-year-old male patient with buttock pain and back pain radiating to the legs. [Methods] A plain anteroposterior radiograph of the pelvis revealed numerous round and oval sclerotic bone areas of varying size. Investigation of the knee joints showed similar findings, and the patient was diagnosed with osteopoikilosis. Lumbar magnetic resonance images showed spinal stenosis and degenerative changes in his lumbar facet joints. Magnetic resonance images of the sacroiliac joints showed bilateral involvement with narrowing of both sacroiliac joints, nodular multiple sclerotic foci, and contrast enhancement in both joint spaces and periarticular areas. HLA B-27 test was negative. [Results] The patient was diagnosed with osteopoikilosis, seronegative spondyloarthritis, and spinal stenosis. Treatment included asemetasin twice daily and exercise therapy. [Conclusion] Symptomatic patients with osteopoikilosis should be investigated for other possible coexisting medical conditions; this will shorten the times to diagnosis and treatment. PMID:26157277

  13. The Ecohydrologic Role of Coexistence and Competition in Semiarid Hillslopes

    NASA Astrophysics Data System (ADS)

    Soltanjalili, M. J.; Saco, P. M.; Willgoose, G. R.

    2015-12-01

    Through its influence on runoff and erosion-deposition processes, vegetation remarkably regulates different aspects of landscape dynamics. Here, the influence of different plant functional traits on the coexistence of different species in arid and semi-arid regions with patchy vegetation is investigated using an ecohydrology model. The model simulates coevolving changes in biomass patterns for two species, as well as overland flow and soil moisture dynamics. Vegetation patterns emerge as a result of facilitation (shading and infiltration) and competition mechanisms as well as varying seed dispersal strategies. The results show that the survival of only one species or the coexistence of both species not only strongly depends on environmental stresses, but also on differences in hillslope micro and macro topography. These vegetation patterns have very different hydrologic signatures and the potential to trigger remarkably different geomorphic responses. Based on these results we establish new hypothesis that will be used to further investigate the role of plant interspecific and intraspecific feedbacks on landscape coevolution processes.

  14. Requirements for plant coexistence through pollination niche partitioning.

    PubMed

    Benadi, Gita

    2015-07-07

    Plant-pollinator interactions are often thought to have been a decisive factor in the diversification of flowering plants, but to be of little or no importance for the maintenance of existing plant diversity. In a recent opinion paper, Pauw (2013 Trends Ecol. Evol. 28, 30-37. (doi:10.1016/j.tree.2012.07.019)) challenged this view by proposing a mechanism of diversity maintenance based on pollination niche partitioning. In this article, I investigate under which conditions the mechanism suggested by Pauw can promote plant coexistence, using a mathematical model of plant and pollinator population dynamics. Numerical simulations show that this mechanism is most effective when the costs of searching for flowers are low, pollinator populations are strongly limited by resources other than pollen and nectar, and plant-pollinator interactions are sufficiently specialized. I review the empirical literature on these three requirements, discuss additional factors that may be important for diversity maintenance through pollination niche partitioning, and provide recommendations on how to detect this coexistence mechanism in natural plant communities.

  15. Plant coexistence alters terpene emission and content of Mediterranean species.

    PubMed

    Ormeño, Elena; Fernandez, Catherine; Mévy, Jean-Philippe

    2007-03-01

    There is evidence that secondary metabolism may modulate plant interactions and is modified by different biotic stress agents, such as herbivores or pathogens. However, it is poorly understood whether secondary metabolism is altered during competition among plants. The intraspecific and interspecific coexistence of some Mediterranean potted seedlings, namely Rosmarinus officinalis, Pinus halepensis, Cistus albidus and Quercus coccifera was investigated through their terpene accumulation within leaves (except for Q. coccifera, a non-storing species) and terpene emissions (for all species). Competition had both positive and negative effects for both terpene emissions and content, depending on the species a seedling coexisted with. For R. officinalis, terpene concentrations (1.8-cineole and camphor) and terpene emissions (camphene, camphor and overall monoterpenes) were lower when the neighbour species was P. halepensis. For C. albidus, no changes were observed in its content, while the overall sesquiterpene emissions (70% of total emissions) were reduced in all competition conditions, except in intraspecific competition. In the case of P. halepensis, the highest terpene content occurred when it grew with C. albidus, and in intraspecific competition, while its emissions were reduced under these conditions. Only emissions of Q. coccifera showed no significant changes in the different competition treatments.

  16. Predicting future coexistence in a North American ant community

    PubMed Central

    Bewick, Sharon; Stuble, Katharine L; Lessard, Jean-Phillipe; Dunn, Robert R; Adler, Frederick R; Sanders, Nathan J

    2014-01-01

    Global climate change will remodel ecological communities worldwide. However, as a consequence of biotic interactions, communities may respond to climate change in idiosyncratic ways. This makes predictive models that incorporate biotic interactions necessary. We show how such models can be constructed based on empirical studies in combination with predictions or assumptions regarding the abiotic consequences of climate change. Specifically, we consider a well-studied ant community in North America. First, we use historical data to parameterize a basic model for species coexistence. Using this model, we determine the importance of various factors, including thermal niches, food discovery rates, and food removal rates, to historical species coexistence. We then extend the model to predict how the community will restructure in response to several climate-related changes, such as increased temperature, shifts in species phenology, and altered resource availability. Interestingly, our mechanistic model suggests that increased temperature and shifts in species phenology can have contrasting effects. Nevertheless, for almost all scenarios considered, we find that the most subordinate ant species suffers most as a result of climate change. More generally, our analysis shows that community composition can respond to climate warming in nonintuitive ways. For example, in the context of a community, it is not necessarily the most heat-sensitive species that are most at risk. Our results demonstrate how models that account for niche partitioning and interspecific trade-offs among species can be used to predict the likely idiosyncratic responses of local communities to climate change. PMID:24963378

  17. Plant functional traits and the multidimensional nature of species coexistence

    PubMed Central

    Kraft, Nathan J. B.; Godoy, Oscar; Levine, Jonathan M.

    2015-01-01

    Understanding the processes maintaining species diversity is a central problem in ecology, with implications for the conservation and management of ecosystems. Although biologists often assume that trait differences between competitors promote diversity, empirical evidence connecting functional traits to the niche differences that stabilize species coexistence is rare. Obtaining such evidence is critical because traits also underlie the average fitness differences driving competitive exclusion, and this complicates efforts to infer community dynamics from phenotypic patterns. We coupled field-parameterized mathematical models of competition between 102 pairs of annual plants with detailed sampling of leaf, seed, root, and whole-plant functional traits to relate phenotypic differences to stabilizing niche and average fitness differences. Single functional traits were often well correlated with average fitness differences between species, indicating that competitive dominance was associated with late phenology, deep rooting, and several other traits. In contrast, single functional traits were poorly correlated with the stabilizing niche differences that promote coexistence. Niche differences could only be described by combinations of traits, corresponding to differentiation between species in multiple ecological dimensions. In addition, several traits were associated with both fitness differences and stabilizing niche differences. These complex relationships between phenotypic differences and the dynamics of competing species argue against the simple use of single functional traits to infer community assembly processes but lay the groundwork for a theoretically justified trait-based community ecology. PMID:25561561

  18. Coexistence of interacting opinions in a generalized Sznajd model.

    PubMed

    Timpanaro, André M; Prado, Carmen P C

    2011-08-01

    The Sznajd model is a sociophysics model that mimics the propagation of opinions in a closed society, where the interactions favor groups of agreeing people. It is based in the Ising and Potts ferromagnetic models and, although the original model used only linear chains, it has since been adapted to general networks. This model has a very rich transient, which has been used to model several aspects of elections, but its stationary states are always consensus states. In order to model more complex behaviors, we have, in a recent work, introduced the idea of biases and prejudices to the Sznajd model by generalizing the bounded confidence rule, which is common to many continuous opinion models, to what we called confidence rules. In that work we have found that the mean field version of this model (corresponding to a complete network) allows for stationary states where noninteracting opinions survive, but never for the coexistence of interacting opinions. In the present work, we provide networks that allow for the coexistence of interacting opinions for certain confidence rules. Moreover, we show that the model does not become inactive; that is, the opinions keep changing, even in the stationary regime. This is an important result in the context of understanding how a rule that breeds local conformity is still able to sustain global diversity while avoiding a frozen stationary state. We also provide results that give some insights on how this behavior approaches the mean field behavior as the networks are changed.

  19. Coexistence of ferromagnetism and superconductivity in YBCO nanoparticles.

    PubMed

    Zhu, Zhonghua; Gao, Daqiang; Dong, Chunhui; Yang, Guijin; Zhang, Jing; Zhang, Jinlin; Shi, Zhenhua; Gao, Hua; Luo, Honggang; Xue, Desheng

    2012-03-21

    Nanoparticles of superconducting YBa(2)Cu(3)O(7-δ) were synthesized via a citrate pyrolysis technique. Room temperature ferromagnetism was revealed in the samples by a vibrating sample magnetometer. Electron spin resonance spectra at selected temperatures indicated that there is a transition from the normal to the superconducting state at temperatures below 100 K. The M-T curves with various applied magnetic fields showed that the superconducting transition temperatures are 92 K and 55 K for the air-annealed and the post-annealed samples, respectively. Compared to the air-annealed sample, the saturation magnetization of the sample by reheating the air-annealed one in argon atmosphere is enhanced but its superconductivity is weakened, which implies that the ferromagnetism maybe originates from the surface oxygen defects. By superconducting quantum interference device measurements, we further confirmed the ferromagnetic behavior at high temperatures and interesting upturns in field cooling magnetization curves within the superconducting region are found. We attributed the upturn phenomena to the coexistence of ferromagnetism and superconductivity at low temperatures. Room temperature ferromagnetism of superconducting YBa(2)Cu(3)O(7-δ) nanoparticles has been observed in some previous related studies, but the issue of the coexistence of ferromagnetism and superconductivity within the superconducting region is still unclear. In the present work, it will be addressed in detail. The cooperation phenomena found in the spin-singlet superconductors will help us to understand the nature of superconductivity and ferromagnetism in more depth.

  20. Explosive synchronization coexists with classical synchronization in the Kuramoto model

    SciTech Connect

    Danziger, Michael M. Havlin, Shlomo; Moskalenko, Olga I.; Kurkin, Semen A.; Zhang, Xiyun; Boccaletti, Stefano

    2016-06-15

    Explosive synchronization has recently been reported in a system of adaptively coupled Kuramoto oscillators, without any conditions on the frequency or degree of the nodes. Here, we find that, in fact, the explosive phase coexists with the standard phase of the Kuramoto oscillators. We determine this by extending the mean-field theory of adaptively coupled oscillators with full coupling to the case with partial coupling of a fraction f. This analysis shows that a metastable region exists for all finite values of f > 0, and therefore explosive synchronization is expected for any perturbation of adaptively coupling added to the standard Kuramoto model. We verify this theory with GPU-accelerated simulations on very large networks (N ∼ 10{sup 6}) and find that, in fact, an explosive transition with hysteresis is observed for all finite couplings. By demonstrating that explosive transitions coexist with standard transitions in the limit of f → 0, we show that this behavior is far more likely to occur naturally than was previously believed.