113,996 research outputs found
Neutron halo in deformed nuclei from a relativistic Hartree-Bogoliubov model in a Woods-Saxon basis
Halo phenomenon in deformed nuclei is studied by using a fully
self-consistent deformed relativistic Hartree-Bogoliubov model in a spherical
Woods-Saxon basis with the proper asymptotic behavior at large distance from
the nuclear center. Taking a deformed neutron-rich and weakly bound nucleus
Mg as an example and by examining contributions of the halo, deformation
effects, and large spatial extensions, we show a decoupling of the halo
orbitals from the deformation of the core.Comment: 6 pages, 2 figures, to appear in the proceedings of the International
Nuclear Physics Conference (INPC 2010), July 4-9 2010, Vancouve
Supernova bound on keV-mass sterile neutrinos reexamined
Active-sterile neutrino mixing is strongly constrained for m_s > 100 keV to
avoid excessive energy losses from supernova cores. For smaller m_s, matter
effects suppress the effective mixing angle except for a resonant range of
energies where it is enhanced. We study the case of \nu_tau-\nu_s-mixing where
a \nu_tau-\bar\nu_tau asymmetry builds up due to the strong excess of \nu_s
over \bar\nu_s emission or vice versa, reducing the overall emission rate. In
the warm dark matter range m_s < 10 keV the mixing angle is essentially
unconstrained.Comment: 6 pages, 4 figures; minor changes, references updated, matches the
published versio
Statistical significance of rich-club phenomena in complex networks
We propose that the rich-club phenomena in complex networks should be defined
in the spirit of bootstrapping, in which a null model is adopted to assess the
statistical significance of the rich-club detected. Our method can be served as
a definition of rich-club phenomenon and is applied to analyzing three real
networks and three model networks. The results improve significantly compared
with previously reported results. We report a dilemma with an exceptional
example, showing that there does not exist an omnipotent definition for the
rich-club phenomenon.Comment: 3 Revtex pages + 5 figure
Optimal squeezing, pure states, and amplification of squeezing in resonance fluorescence
It is shown that 100% squeezed output can be produced in the resonance
fluorescence from a coherently driven two-level atom interacting with a
squeezed vacuum. This is only possible for squeezed input, and is
associated with a pure atomic state, i.e., a completely polarized state. The
quadrature for which optimal squeezing occurs depends on the squeezing phase
the Rabi frequency and the atomic detuning . Pure
states are described for arbitrary not just or as in
previous work. For small values of there may be a greater degree of
squeezing in the output field than the input - i.e., we have squeezing
amplification.Comment: 6 pages & 7 figures, Submitted to Phys. Rev.
An analysis of dynamical suppression of spontaneous emission
It has been shown recently [see, for example, S.-Y. Zhu and M. O. Scully,
Phys. Rev. Lett. {\bf 76}, 388 (1996)] that a dynamical suppression of
spontaneous emission can occur in a three-level system when an external field
drives transitions between a metastable state and {\em two} decaying states.
What is unusual in the decay scheme is that the decaying states are coupled
directly by the vacuum radiation field. It is shown that decay dynamics
required for total suppression of spontaneous emission necessarily implies that
the level scheme is isomorphic to a three-level lambda system, in which the
lower two levels are {\em both} metastable, and each is coupled to the decaying
state. As such, the total suppression of spontaneous emission can be explained
in terms of conventional dark states and coherent population trapping.Comment: 8 pages, 3 figure
No association of CTLA-4 polymorphisms with susceptibility to Behcet disease
Background: Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a key negative regulator of T lymphocytes and has been shown to be associated with a number of autoimmune diseases. The present study was performed to assess the association between CTLA-4 polymorphisms and Behcet disease (BD) in Chinese patients. Methods: Two hundred and twenty-eight BD patients and 207 controls were analysed for four single nucleotide polymorphisms (SNPs) (21661A/G, 2318C/T, + 49G/A and CT60G/A) in the CTLA-4 gene by PCR-restriction fragment length polymorphism (RFLP) analysis. The association between SNP +49A/G and BD in Chinese population as well as other ethnic groups was analysed by meta-analysis. Results: No association could be detected between CTLA-4 SNPs or haplotypes and BD. Also, no association was observed between CTLA-4 polymorphisms and BD subgroups, stratified by clinical features. A meta-analysis showed that there was no heterogeneity between studies (p = 0.60, I-2 = 0%) and that CTLA-4 SNP + 49 was not associated with BD (overall effect: Z = 0.26, p = 0.79). Conclusion: This study and a meta-analysis failed to demonstrate any association between the tested CTLA-4 polymorphisms and B
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