19,345 research outputs found
Employer-Sponsored Health Insurance: Down, But Not Out
Presents findings from twelve metropolitan areas about employers' efforts to control employee healthcare costs in response to the recession and national healthcare reform by firm size. Projects employer trends through 2014, including greater cost sharing
Quantum spin models for the SU(n)_1 Wess-Zumino-Witten model
We propose 1D and 2D lattice wave functions constructed from the SU(n)_1
Wess-Zumino-Witten (WZW) model and derive their parent Hamiltonians. When all
spins in the lattice transform under SU(n) fundamental representations, we
obtain a two-body Hamiltonian in 1D, including the SU(n) Haldane-Shastry model
as a special case. In 2D, we show that the wave function converges to a class
of Halperin's multilayer fractional quantum Hall states and belongs to chiral
spin liquids. Our result reveals a hidden SU(n) symmetry for this class of
Halperin states. When the spins sit on bipartite lattices with alternating
fundamental and conjugate representations, we provide numerical evidence that
the state in 1D exhibits quantum criticality deviating from the expected
behaviors of the SU(n)_1 WZW model, while in 2D they are chiral spin liquids
being consistent with the prediction of the SU(n)_1 WZW model.Comment: 28 pages, 9 figures, published versio
Observation of indirect ionization of W7+ in an electron-beam ion-trap plasma
In this work, visible and extreme ultraviolet spectra of W7+ are measured
using the high-temperature superconducting electron-beam ion trap (EBIT) at the
Shanghai EBIT Laboratory under extremely low-energy conditions (lower than the
nominal electron-beam energy of 130 eV). The relevant atomic structure is
calculated using the flexible atomic code package based on the relativistic
configuration interaction method. The GRASP2K code, in the framework of the
multiconfiguration Dirac-Hartree-Fock method, is employed as well for
calculating the wavelength of the M1 transition in the ground configuration of
W7+. A line from the W7+ ions is observed at a little higher electron-beam
energy than the ionization potential for W4+, making this line appear to be
from W5+. A hypothesis for the charge-state evolution of W7+ is proposed based
on our experimental and theoretical results; that is, the occurrence of W7+
ions results from indirect ionization caused by stepwise excitation between
some metastable states of lower-charge-state W ions, at the nominal
electron-beam energy of 59 eV
Circumventing embryonic lethality with Lcmt1 deficiency: generation of hypomorphic Lcmt1 mice with reduced protein phosphatase 2A methyltransferase expression and defects in insulin signaling.
Protein phosphatase 2A (PP2A), the major serine/threonine phosphatase in eukaryotic cells, is a heterotrimeric protein composed of structural, catalytic, and targeting subunits. PP2A assembly is governed by a variety of mechanisms, one of which is carboxyl-terminal methylation of the catalytic subunit by the leucine carboxyl methyltransferase LCMT1. PP2A is nearly stoichiometrically methylated in the cytosol, and although some PP2A targeting subunits bind independently of methylation, this modification is required for the binding of others. To examine the role of this methylation reaction in mammalian tissues, we generated a mouse harboring a gene-trap cassette within intron 1 of Lcmt1. Due to splicing around the insertion, Lcmt1 transcript and LCMT1 protein levels were reduced but not eliminated. LCMT1 activity and methylation of PP2A were reduced in a coordinate fashion, suggesting that LCMT1 is the only PP2A methyltransferase. These mice exhibited an insulin-resistance phenotype, indicating a role for this methyltransferase in signaling in insulin-sensitive tissues. Tissues from these animals will be vital for the in vivo identification of methylation-sensitive substrates of PP2A and how they respond to differing physiological conditions
Projected entangled-pair states can describe chiral topological states
We show that Projected Entangled-Pair States (PEPS) in two spatial dimensions
can describe chiral topological states by explicitly constructing a family of
such states with a non-trivial Chern number. They are ground states of two
different kinds of free-fermion Hamiltonians: (i) local and gapless; (ii)
gapped, but with hopping amplitudes that decay according to a power law. We
derive general conditions on topological free fermionic PEPS which show that
they cannot correspond to exact ground states of gapped, local parent
Hamiltonians, and provide numerical evidence demonstrating that they can
nevertheless approximate well the physical properties of topological insulators
with local Hamiltonians at arbitrary temperatures.Comment: v2: minor changes, references added. v3: accepted version,
Journal-Ref adde
Chiral projected entangled-pair state with topological order
We show that projected entangled-pair states (PEPS) can describe chiral
topologically ordered phases. For that, we construct a simple PEPS for spin-1/2
particles in a two-dimensional lattice. We reveal a symmetry in the local
projector of the PEPS that gives rise to the global topological character. We
also extract characteristic quantities of the edge conformal field theory using
the bulk-boundary correspondence.Comment: 11 pages, 7 figure
Bandwidth and density for block graphs
The bandwidth of a graph G is the minimum of the maximum difference between
adjacent labels when the vertices have distinct integer labels. We provide a
polynomial algorithm to produce an optimal bandwidth labeling for graphs in a
special class of block graphs (graphs in which every block is a clique), namely
those where deleting the vertices of degree one produces a path of cliques. The
result is best possible in various ways. Furthermore, for two classes of graphs
that are ``almost'' caterpillars, the bandwidth problem is NP-complete.Comment: 14 pages, 9 included figures. Note: figures did not appear in
original upload; resubmission corrects thi
A Coupled AKNS-Kaup-Newell Soliton Hierarchy
A coupled AKNS-Kaup-Newell hierarchy of systems of soliton equations is
proposed in terms of hereditary symmetry operators resulted from Hamiltonian
pairs. Zero curvature representations and tri-Hamiltonian structures are
established for all coupled AKNS-Kaup-Newell systems in the hierarchy.
Therefore all systems have infinitely many commuting symmetries and
conservation laws. Two reductions of the systems lead to the AKNS hierarchy and
the Kaup-Newell hierarchy, and thus those two soliton hierarchies also possess
tri-Hamiltonian structures.Comment: 15 pages, late
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