21,125 research outputs found
Evaluation of a New Recombinant K39 Rapid Diagnostic Test for Sudanese Visceral Leishmaniasis.
A new rK39 rapid diagnostic dipstick test (DiaMed-IT-Leish) was compared with aspiration and a direct agglutination test (DAT) for diagnosis of visceral leishmaniasis (VL) in 201 parasitologically confirmed cases, 133 endemic controls, and in 356 clinical suspects in disease-endemic and -epidemic areas in Sudan. The sensitivity of the rK39 test in parasitologically confirmed VL cases was 90%, whereas the specificity in disease-endemic controls was 99%. The sensitivity of the DAT was 98%. In clinically suspected cases, the sensitivity of the rK39 test was 81% and the specificity was 97%. When compared with the diagnostic protocol based on the DAT and aspiration used by Médecins sans Frontières in epidemic situations, the positive predictive value was 98%, and the negative predictive value was 71%. This rK39 rapid diagnostic test is suitable for screening as well as diagnosis of VL. Further diagnostic work-up of dipstick-negative patients with clinically suspected VL is important. The ease and convenience of the dipstick test will allow decentralization and improved access to care in disease-endemic areas in Sudan
Reconstructing Seesaws
We explore some aspects of "reconstructing" the heavy singlet sector of
supersymmetric type I seesaw models, for two, three or four singlets. We work
in the limit where one light neutrino is massless. In an ideal world, where
selected coefficients of the TeV-scale effective Lagrangian could be measured
with arbitrary accuracy, the two-singlet case can be reconstructed, two three
or more singlets can be differentiated, and an inverse seesaw with four
singlets can be reconstructed. In a more realistic world, we estimate \ell_\a
\to \ell_\b \gamma expectations with a "Minimal-Flavour-Violation-like"
ansatz, which gives a relation between ratios of the three branching ratios.
The two singlet model predicts a discrete set of ratios.Comment: 14 page
Neutrino Physics: Open Theoretical Questions
We know that neutrino mass and mixing provide a window to physics beyond the
Standard Model. Now this window is open, at least partly. And the questions
are: what do we see, which kind of new physics, and how far "beyond"? I
summarize the present knowledge of neutrino mass and mixing, and then formulate
the main open questions. Following the bottom-up approach, properties of the
neutrino mass matrix are considered. Then different possible ways to uncover
the underlying physics are discussed. Some results along the line of: see-saw,
GUT and SUSY GUT are reviewed.Comment: 17 pages, latex, 12 figures. Talk given at the XXI International
Symposium on Lepton and Photon Interactions at High Energies, ``Lepton Photon
2003", August 11-16, 2003 - Fermilab, Batavia, IL US
Effective Lagrangian Approach to the Fermion Mass Problem
An effective theory is proposed, combining the standard gauge group
with a horizontal discrete
symmetry. By assigning appropriate charges under this discrete symmetry to the
various fermion fields and to (at least) two Higgs doublets, the broad spread
of the fermion mass and mixing angle spectrum can be explained as a result of
suppressed, non-renormalisable terms. A particular model is constructed which
achieves the above while simultaneously suppressing neutral Higgs-induced
flavour-changing processes.Comment: 21 pages, UM-P-93/81, latex file, 1 figure available on reques
Effective Interaction Techniques for the Gamow Shell Model
We apply a contour deformation technique in momentum space to the newly
developed Gamow shell model, and study the drip-line nuclei 5He, 6He and 7He. A
major problem in Gamow shell-model studies of nuclear many-body systems is the
increasing dimensionality of many-body configurations due to the large number
of resonant and complex continuum states necessary to reproduce bound and
resonant state energies. We address this problem using two different effective
operator approaches generalized to the complex momentum plane. These are the
Lee-Suzuki similarity transformation method for complex interactions and the
multi-reference perturbation theory method. The combination of these two
approaches results in a large truncation of the relevant configurations
compared with direct diagonalization. This offers interesting perspectives for
studies of weakly bound systems.Comment: 18 pages, 17 figs, Revtex
Scotland, Catalonia and the “right” to self-determination: a comment suggested by Kathryn Crameri’s “Do Catalans Have the Right to Decide?
No abstract available
Topology and Phases in Fermionic Systems
There can exist topological obstructions to continuously deforming a gapped
Hamiltonian for free fermions into a trivial form without closing the gap.
These topological obstructions are closely related to obstructions to the
existence of exponentially localized Wannier functions. We show that by taking
two copies of a gapped, free fermionic system with complex conjugate
Hamiltonians, it is always possible to overcome these obstructions. This allows
us to write the ground state in matrix product form using Grassman-valued bond
variables, and show insensitivity of the ground state density matrix to
boundary conditions.Comment: 4 pages, see also arxiv:0710.329
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