27,014 research outputs found
Reflection matrices for the vertex model
The graded reflection equation is investigated for the
vertex model. We have found four classes of diagonal
solutions and twelve classes of non-diagonal ones. The number of free
parameters for some solutions depends on the number of bosonic and fermionic
degrees of freedom considered.Comment: 30 page
Finance and performance of Portuguese hospitals
This study analyses the impact of changing systems of finance on the performance of hospitals in Portugal, specifically in terms of costs per admission and per patient day, average length of stay and the number of admissions. The study is based on panel data (36 hospitals over a ten-year period), used to estimate cost functions. It is concluded that costs per admission decreased over the period in question, principally due to declining length of stay.DRG, financing systems, hospital, Portugal, prospective payment
Cell Therapy for Type 1 Diabetes
Acknowledgements The work described in this review was supported by a grant from the MRC. K.R.M. is supported by a fellowship from the Scottish Translational Medicines and Therapeutics Initiative through the Wellcome Trust.Peer reviewedPublisher PD
Competition between local potentials and attractive particle-particle interactions in superlattices
Naturally occuring or man-made systems displaying periodic spatial
modulations of their properties on a nanoscale constitute superlattices. Such
modulated structures are important both as prototypes of simple
nanotechnological devices and as particular examples of emerging spatial
inhomogeneity in interacting many-electron systems. Here we investigate the
effect different types of modulation of the system parameters have on the
ground-state energy and the charge-density distribution of the system. The
superlattices are described by the inhomogeneous attractive Hubbard model, and
the calculations are performed by density-functional and density-matrix
renormalization group techniques. We find that modulations in local electric
potentials are much more effective in shaping the system's properties than
modulations in the attractive on-site interaction. This is the same conclusions
we previously (Phys. Rev. B 71, 125130) obtained for repulsive interactions,
suggesting that it is not an artifact of a specific state, but a general
property of modulated structures.Comment: 8 pages, 2 figure
Area Quantization in Quasi-Extreme Black Holes
We consider quasi-extreme Kerr and quasi-extreme Schwarzschild-de Sitter
black holes. From the known analytical expressions obtained for their
quasi-normal modes frequencies, we suggest an area quantization prescription
for those objects.Comment: Final version to appear in Mod. Phys. Lett.
Probing embedded star clusters in the HII complex NGC 6357 with VVV
NGC 6357 is an active star-forming region located in the Sagittarius arm
displaying several star clusters, which makes it a very interesting target to
investigate star formation and early cluster evolution. We explore NGC 6357
with the "VISTA Variables in the V\'ia a L\'actea" (VVV) photometry of seven
embedded clusters (ECs), and one open cluster (OC) projected in the outskirts
of the complex.Photometric and structural properties (age, reddening, distance,
core and total radii) of the star clusters are derived. VVV saturated stars are
replaced by their 2MASS counterparts. Field-decontaminated VVV photometry is
used to analyse Colour-Magnitude Diagrams (CMDs), stellar radial density
profiles (RDPs) and determine astrophysical parameters. We report the discovery
of four ECs and one intermediate-age cluster in the complex area. We derive a
revised distance estimate for NGC 6357 of 1.780.1 kpc based on the cluster
CMD morphologies. Among the ECs, one contains the binary star the WR 93, while
the remaining ones are dominated by pre-main sequence (PMS) stars,
young-stellar objects (YSO) and/or and have a developed main sequence. These
features reflect a significant age spread among the clusters. Evidence is found
that the relatively populous cluster Pismis 24 hosts two subclusters.Comment: This article will be published in the A&A. 11 pages, 15 figures and 3
table
Friedel oscillations in one-dimensional metals: from Luttinger's theorem to the Luttinger liquid
Charge density and magnetization density profiles of one-dimensional metals
are investigated by two complementary many-body methods: numerically exact
(Lanczos) diagonalization, and the Bethe-Ansatz local-density approximation
with and without a simple self-interaction correction. Depending on the
magnetization of the system, local approximations reproduce different Fourier
components of the exact Friedel oscillations.Comment: 3 pages, 3 figures, Manuscript accepted by Journal of Magnetism and
Magnetic Materials, special issue for LAWMMM 2007 conferenc
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