21 research outputs found
Del Pezzo Surfaces and Affine 7-brane Backgrounds
A map between string junctions in the affine 7-brane backgrounds and vector
bundles on del Pezzo surfaces is constructed using mirror symmetry. It is shown
that the lattice of string junctions with support on an affine 7-brane
configuration is isomorphic to the K-theory group of the corresponding del
Pezzo surface. This isomorphism allows us to construct a map between the states
of the N=2, D=4 theories with E_N global symmetry realized in two different
ways in Type IIB and Type IIA string theory. A subgroup of the SL(2,Z) symmetry
of the \hat{E}_9 7-brane background appears as the Fourier-Mukai transform
acting on the D-brane configurations realizing vector bundles on elliptically
fibered B_9.Comment: 19 pages, LaTeX, 2 eps figures. v2: minor changes, version to appear
in JHE
D-branes in Nonabelian Orbifolds with Discrete Torsion
We study IIB string theory on the orbifold R^8/Gamma with discrete torsion
where Gamma is an arbitrary subgroup of U(4). We extend some previously known
identities for discrete torsion in abelian groups to nonabelian groups. We
construct explicit formulas for a large class of fractional D-brane states and
prove that the physical states are classified by projective representations of
the orbifold group as predicted originally by Douglas. The boundary states are
found to be linear combinations of Ishibashi states with the coefficients being
characters of the projective representations.Comment: 21 pages LaTeX, one eps figur
The Requirements for Ontologies in Medical Data Integration: A Case Study
Evidence-based medicine is critically dependent on three sources of
information: a medical knowledge base, the patients medical record and
knowledge of available resources, including where appropriate, clinical
protocols. Patient data is often scattered in a variety of databases and may,
in a distributed model, be held across several disparate repositories.
Consequently addressing the needs of an evidence-based medicine community
presents issues of biomedical data integration, clinical interpretation and
knowledge management. This paper outlines how the Health-e-Child project has
approached the challenge of requirements specification for (bio-) medical data
integration, from the level of cellular data, through disease to that of
patient and population. The approach is illuminated through the requirements
elicitation and analysis of Juvenile Idiopathic Arthritis (JIA), one of three
diseases being studied in the EC-funded Health-e-Child project.Comment: 6 pages, 1 figure. Presented at the 11th International Database
Engineering & Applications Symposium (Ideas2007). Banff, Canada September
200