47,840 research outputs found
Asymptotics of neutron Cooper pair in weakly bound nuclei
Asymptotic form of neutron Cooper pair penetrating to the exterior of nuclear
surface is investigated with the Bogoliubov theory for the superfluid Fermions.
Based on a two-particle Schr\"{o}dinger equation governing the Cooper pair wave
function and systematic studies for both weakly bound and stable nuclei, the
Cooper pair is shown to be spatially correlated even in the asymptotic large
distance limit, and the penetration length of the pair condensate is revealed
to be universally governed by the two-neutron separation energy and
the di-neutron mass
Pair correlation of giant halo nuclei in continuum Skyrme-Hartree-Fock-Bogoliubov theory
The giant halos predicted in neutron-rich Zr isotopes with are
investigated by using the self-consistent continuum Skyrme
Hartree-Fock-Bogoliubov approach, in which the asymptotic behavior of continuum
quasiparticle states is properly treated by the Green's function method. We
study in detail the neutron pair correlation involved in the giant halo by
analyzing the asymptotic exponential tail of the neutron pair condensate (pair
density) in addition to that of the neutron particle density. The neutron
quasiparticle spectra associated with these giant halo nuclei are examined. It
is found that the asymptotic exponential tail of the neutron pair condensate is
dominated by non-resonant continuum quasiparticle states corresponding to the
scattering states with low asymptotic kinetic energy. This is in contrast to
the asymptotic tail of the neutron density, whose main contributions arise from
the resonant quasiparticle states corresponding to the weakly-bound
single-particle orbits and resonance orbits in the Hartree-Fock potential
Generalized MICZ-Kepler Problems and Unitary Highest Weight Modules
For each integer , we demonstrate that a -dimensional
generalized MICZ-Kepler problem has an \mr{Spin}(2, 2n+2) dynamical symmetry
which extends the manifest \mr{Spin}(2n+1) symmetry. The Hilbert space of
bound states is shown to form a unitary highest weight \mr{Spin}(2,
2n+2)-module which occurs at the first reduction point in the
Enright-Howe-Wallach classification diagram for the unitary highest weight
modules. As a byproduct, we get a simple geometric realization for such a
unitary highest weight \mr{Spin}(2, 2n+2)-module.Comment: 27 pages, Refs. update
Transformation of \u3cem\u3eTetrahymena thermophila\u3c/em\u3e with Hypermethylated rRNA Genes
The extrachromosomal rRNA genes (rDNA) of Tetrahymena thermophila contain 0.4% N6-methyladenine. C3 strain rDNA was isolated, hypermethylated in vitro, and microinjected into B strain host cells. Clonal cell lines were established, and transformants were selected on the basis of resistance to paromomycin, conferred by the injected rDNA. The effects of methylation by three enzymes which methylate the sequence 5\u27-NAT-3\u27, the dam, EcoRI, and ClaI methylases, were tested. Hypermethylation of the injected rDNA had no effect on transformation efficiency relative to mock-methylated controls. The injected C3 strain rDNA efficiently replaced host rDNA as the major constituent of the population of rDNA molecules. Hypermethylation of the injected DNA was not maintained through 20 to 25 cell generations
Digital optical phase conjugation of fluorescence in turbid tissue
We demonstrate a method for phase conjugating fluorescence. Our method, called reference free digital optical phase conjugation, can conjugate extremely weak, incoherent optical signals. It was used to phase conjugate fluorescent light originating from a bead covered with 0.5 mm of light-scattering tissue. The phase conjugated beam refocuses onto the bead and causes a local increase of over two orders of magnitude in the light intensity. Potential applications are in imaging, optical trapping, and targeted photochemical activation inside turbid tissue
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