454 research outputs found
Real time antimicrobial resistance surveillance in critical care: Identifying outbreaks of carbapenem resistant gram negative bacteria from routinely collected data
Quantum Foam and Topological Strings
We find an interpretation of the recent connection found between topological
strings on Calabi-Yau threefolds and crystal melting: Summing over statistical
mechanical configuration of melting crystal is equivalent to a quantum
gravitational path integral involving fluctuations of Kahler geometry and
topology. We show how the limit shape of the melting crystal emerges as the
average geometry and topology of the quantum foam at the string scale. The
geometry is classical at large length scales, modified to a smooth limit shape
dictated by mirror geometry at string scale and is a quantum foam at area
scales g_s \alpha'.Comment: 55 page
Application of the National Osteoporosis Foundation Guidelines to postmenopausal women and men: the Framingham Osteoporosis Study.
Summary
We applied the 2008 National Osteoporosis Foundation (NOF) Guidelines to Framingham Osteoporosis Study participants and found nearly one half of Caucasian postmenopausal women and one sixth of men aged 50 years and older would be recommended for osteoporosis treatment. Given the high proportion of persons recommended for treatment, NOF Guidelines may need to be re-evaluated with respect to budget impact.
Introduction
Little is known about the public health impact of the NOF Guidelines. Therefore, we determined the proportion of US Caucasians recommended for treatment of osteoporosis according to NOF Guidelines (2003 and 2008).
Methods
One thousand nine hundred and forty-six postmenopausal women and 1,681 men aged ≥50 years from the Framingham Study with information on bone mineral density (1987–2001) were included. Information on clinical predictors was used to estimate the 10-year probability of hip and major osteoporotic fracture by FRAX® (version 3.0).
Results
Overall proportion of women meeting treatment criterion was less when the 2008 NOF Guidelines were applied (41.1%) compared with 2003 Guidelines (47.8%). The proportion of women aged 75 years increased slightly (78.3% in 2003, 86.0% in 2008). Seventeen percent of men aged ≥50 years met treatment criterion (2.5% aged 50–64 years, 49.8% aged >75 years).
Conclusions
Nearly one half of Caucasian postmenopausal women and one sixth of men aged 50 years and older would be recommended for osteoporosis treatment according to 2008 NOF Guidelines. Given the high proportion of persons recommended for treatment, NOF Guidelines may need to be re-evaluated with respect to budget impact
Vector Bundle Moduli and Small Instanton Transitions
We give the general presciption for calculating the moduli of irreducible,
stable SU(n) holomorphic vector bundles with positive spectral covers over
elliptically fibered Calabi-Yau threefolds. Explicit results are presented for
Hirzebruch base surfaces B=F_r. The transition moduli that are produced by
chirality changing small instanton phase transitions are defined and
specifically enumerated. The origin of these moduli, as the deformations of the
spectral cover restricted to the ``lift'' of the horizontal curve of the
M5-brane, is discussed. We present an alternative description of the transition
moduli as the sections of rank n holomorphic vector bundles over the M5-brane
curve and give explicit examples. Vector bundle moduli appear as gauge singlet
scalar fields in the effective low-energy actions of heterotic superstrings and
heterotic M-theory.Comment: 52 pages, LATEX, corrected typo
Vector Bundle Moduli Superpotentials in Heterotic Superstrings and M-Theory
The non-perturbative superpotential generated by a heterotic superstring
wrapped once around a genus-zero holomorphic curve is proportional to the
Pfaffian involving the determinant of a Dirac operator on this curve. We show
that the space of zero modes of this Dirac operator is the kernel of a linear
mapping that is dependent on the associated vector bundle moduli. By explicitly
computing the determinant of this map, one can deduce whether or not the
dimension of the space of zero modes vanishes. It is shown that this
information is sufficient to completely determine the Pfaffian and, hence, the
non-perturbative superpotential as explicit holomorphic functions of the vector
bundle moduli. This method is illustrated by a number of non-trivial examples.Comment: 81 pages, LaTeX, corrected typo
Residues and World-Sheet Instantons
We reconsider the question of which Calabi-Yau compactifications of the
heterotic string are stable under world-sheet instanton corrections to the
effective space-time superpotential. For instance, compactifications described
by (0,2) linear sigma models are believed to be stable, suggesting a remarkable
cancellation among the instanton effects in these theories. Here, we show that
this cancellation follows directly from a residue theorem, whose proof relies
only upon the right-moving world-sheet supersymmetries and suitable compactness
properties of the (0,2) linear sigma model. Our residue theorem also extends to
a new class of "half-linear" sigma models. Using these half-linear models, we
show that heterotic compactifications on the quintic hypersurface in CP^4 for
which the gauge bundle pulls back from a bundle on CP^4 are stable. Finally, we
apply similar ideas to compute the superpotential contributions from families
of membrane instantons in M-theory compactifications on manifolds of G_2
holonomy.Comment: 47 page
The New Marine Recreational Fishery Statistics Survey method for estimating Charter Boat Fishing effort
Topological String Amplitudes, Complete Intersection Calabi-Yau Spaces and Threshold Corrections
We present the most complete list of mirror pairs of Calabi-Yau complete
intersections in toric ambient varieties and develop the methods to solve the
topological string and to calculate higher genus amplitudes on these compact
Calabi-Yau spaces. These symplectic invariants are used to remove redundancies
in examples. The construction of the B-model propagators leads to compatibility
conditions, which constrain multi-parameter mirror maps. For K3 fibered
Calabi-Yau spaces without reducible fibers we find closed formulas for all
genus contributions in the fiber direction from the geometry of the fibration.
If the heterotic dual to this geometry is known, the higher genus invariants
can be identified with the degeneracies of BPS states contributing to
gravitational threshold corrections and all genus checks on string duality in
the perturbative regime are accomplished. We find, however, that the BPS
degeneracies do not uniquely fix the non-perturbative completion of the
heterotic string. For these geometries we can write the topological partition
function in terms of the Donaldson-Thomas invariants and we perform a
non-trivial check of S-duality in topological strings. We further investigate
transitions via collapsing D5 del Pezzo surfaces and the occurrence of free Z2
quotients that lead to a new class of heterotic duals.Comment: 117 pages, 1 Postscript figur
Stability and duality in N=2 supergravity
The BPS-spectrum is known to change when moduli cross a wall of marginal
stability. This paper tests the compatibility of wall-crossing with S-duality
and electric-magnetic duality for N=2 supergravity. To this end, the
BPS-spectrum of D4-D2-D0 branes is analyzed in the large volume limit of
Calabi-Yau moduli space. Partition functions are presented, which capture the
stability of BPS-states corresponding to two constituents with primitive
charges and supported on very ample divisors in a compact Calabi-Yau. These
functions are `mock modular invariant' and therefore confirm S-duality.
Furthermore, wall-crossing preserves electric-magnetic duality, but is shown to
break the `spectral flow' symmetry of the N=(4,0) CFT, which captures the
degrees of freedom of a single constituent.Comment: 25 pages + appendix; v3: final versio
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