982 research outputs found
Application of Quantum Annealing to Nurse Scheduling Problem
Quantum annealing is a promising heuristic method to solve combinatorial
optimization problems, and efforts to quantify performance on real-world
problems provide insights into how this approach may be best used in practice.
We investigate the empirical performance of quantum annealing to solve the
Nurse Scheduling Problem (NSP) with hard constraints using the D-Wave 2000Q
quantum annealing device. NSP seeks the optimal assignment for a set of nurses
to shifts under an accompanying set of constraints on schedule and personnel.
After reducing NSP to a novel Ising-type Hamiltonian, we evaluate the solution
quality obtained from the D-Wave 2000Q against the constraint requirements as
well as the diversity of solutions. For the test problems explored here, our
results indicate that quantum annealing recovers satisfying solutions for NSP
and suggests the heuristic method is sufficient for practical use. Moreover, we
observe that solution quality can be greatly improved through the use of
reverse annealing, in which it is possible to refine a returned results by
using the annealing process a second time. We compare the performance NSP using
both forward and reverse annealing methods and describe how these approach
might be used in practice.Comment: 20 pages, 13 figure
Global network structure of dominance hierarchy of ant workers
Dominance hierarchy among animals is widespread in various species and
believed to serve to regulate resource allocation within an animal group.
Unlike small groups, however, detection and quantification of linear hierarchy
in large groups of animals are a difficult task. Here, we analyse
aggression-based dominance hierarchies formed by worker ants in Diacamma sp. as
large directed networks. We show that the observed dominance networks are
perfect or approximate directed acyclic graphs, which are consistent with
perfect linear hierarchy. The observed networks are also sparse and random but
significantly different from networks generated through thinning of the perfect
linear tournament (i.e., all individuals are linearly ranked and dominance
relationship exists between every pair of individuals). These results pertain
to global structure of the networks, which contrasts with the previous studies
inspecting frequencies of different types of triads. In addition, the
distribution of the out-degree (i.e., number of workers that the focal worker
attacks), not in-degree (i.e., number of workers that attack the focal worker),
of each observed network is right-skewed. Those having excessively large
out-degrees are located near the top, but not the top, of the hierarchy. We
also discuss evolutionary implications of the discovered properties of
dominance networks.Comment: 5 figures, 2 tables, 4 supplementary figures, 2 supplementary table
Gauge-Fixing and Residual Symmetries in Gauge/Gravity Theories with Extra Dimensions
We study compactified pure gauge/gravitational theories with gauge-fixing
terms and show that these theories possess quantum mechanical SUSY-like
symmetries between unphysical degrees of freedom. These residual symmetries are
global symmetries and generated by quantum mechanical N=2 supercharges. Also,
we establish new one-parameter family of gauge choices for higher-dimensional
gravity, and calculate as a check of its validity one graviton exchange
amplitude in the lowest tree-level approximation. We confirm that the result is
indeed -independent and the cancellation of the -dependence is
ensured by the residual symmetries. We also give a simple interpretation of the
vDVZ-discontinuity, which arises in the lowest tree-level approximation, from
the supersymmetric point of view.Comment: REVTeX4, 17 pages, 1 figur
Rayleigh-Taylor instability and mushroom-pattern formation in a two-component Bose-Einstein condensate
The Rayleigh-Taylor instability at the interface in an immiscible
two-component Bose-Einstein condensate is investigated using the mean-field and
Bogoliubov theories. Rayleigh-Taylor fingers are found to grow from the
interface and mushroom patterns are formed. Quantized vortex rings and vortex
lines are then generated around the mushrooms. The Rayleigh-Taylor instability
and mushroom-pattern formation can be observed in a trapped system.Comment: 5 pages, 4 figure
Singularity results for functional equations driven by linear fractional transformations
We consider functional equations driven by linear fractional transformations,
which are special cases of de Rham's functional equations. We consider
Hausdorff dimension of the measure whose distribution function is the solution.
We give a necessary and sufficient condition for singularity. We also show that
they have a relationship with stationary measures.Comment: 14 pages, Title changed, to appear in Journal of Theoretical
Probabilit
Magnetic properties of the Ag-In-rare-earth 1/1 approximants
We have performed magnetic susceptibility and neutron scattering measurements
on polycrystalline Ag-In-RE (RE: rare-earth) 1/1 approximants. In the magnetic
susceptibility measurements, for most of the RE elements, inverse
susceptibility shows linear behaviour in a wide temperature range, confirming
well localized isotropic moments for the RE ions. Exceptionally for the
light RE elements, such as Ce and Pr, non-linear behaviour was observed,
possibly due to significant crystalline field splitting or valence fluctuation.
For RE = Tb, the susceptibility measurement clearly shows a bifurcation of the
field-cooled and zero-field-cooled susceptibility at ~K,
suggesting a spin-glass-like freezing. On the other hand, neutron scattering
measurements detect significant development of short-range antiferromagnetic
spin correlations in elastic channel, which accompanied by a broad peak at
~meV in inelastic scattering spectrum. These features have
striking similarity to those in the Zn-Mg-Tb quasicrystals, suggesting that the
short-range spin freezing behaviour is due to local high symmetry clusters
commonly seen in both the systems.Comment: 14 pages, 12 figure
Capillary instability in a two-component Bose-Einstein condensate
Capillary instability and the resulting dynamics in an immiscible
two-component Bose-Einstein condensate are investigated using the mean-field
and Bogoliubov analyses. A long, cylindrical condensate surrounded by the other
component is dynamically unstable against breakup into droplets due to the
interfacial tension arising from the quantum pressure and interactions. A
heteronuclear system confined in a cigar-shaped trap is proposed for realizing
this phenomenon experimentally.Comment: 7 pages, 6 figure
Effective Therapy Using Voglibose for Nonalcoholic Steatohepatitis in a Patient with Insufficient Dietary and Exercise Therapy: Exploring Other Treatment Possibilities
A 56-year-old Japanese female with a 10-year history of thyroiditis presented to our institution. The laboratory data and clinical findings suggested that the patient had complicated nonalcoholic fatty liver disease or nonalcoholic steatohepatitis (NASH) with autoimmune hepatitis according to the criteria by the application of the International Autoimmune Hepatitis score. The patient could not manage by herself so dietary- and exercise-based treatment was difficult. Accordingly, ursodeoxycholic acid and ezetimibe therapy was started and continued until the performance of a liver needle biopsy to define the diagnosis. However, no improvement in liver function was observed. In addition, pathological findings indicated that the patient had NASH. The patient was finally diagnosed as having NASH. Therefore, voglibose was added to the ursodeoxycholic acid and ezetimibe therapy, and this addition of voglibose actually took effect. The patient's serum aspartate transaminase and alanine aminotransferase levels decreased dramatically. This report is the first to document other treatment possibilities of NASH in a case when dietary therapy is difficult
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