306 research outputs found
Progress using generalized lattice Dirac operators to parametrize the Fixed-Point QCD action
We report on an ongoing project to parametrize the Fixed-Point Dirac operator
for massless quarks, using a very general construction which has arbitrarily
many fermion offsets and gauge paths, the complete Clifford algebra and
satisfies all required symmetries. Optimizing a specific construction with
hypercubic fermion offsets, we present some preliminary results.Comment: Lattice 2000 (Improvement), 9 pages, based on a talk by K.H. and a
poster by T.J. References adde
The construction of generalized Dirac operators on the lattice
We discuss the steps to construct Dirac operators which have arbitrary
fermion offsets, gauge paths, a general structure in Dirac space and satisfy
the basic symmetries (gauge symmetry, hermiticity condition, charge
conjugation, hypercubic rotations and reflections) on the lattice. We give an
extensive set of examples and offer help to add further structures.Comment: 19 pages, latex, maple code attache
Retinal gene therapy with a large MYO7A cDNA using adeno-associated virus.
Usher 1 patients are born profoundly deaf and then develop retinal degeneration. Thus they are readily identified before the onset of retinal degeneration, making gene therapy a viable strategy to prevent their blindness. Here, we have investigated the use of adeno-associated viruses (AAVs) for the delivery of the Usher 1B gene, MYO7A, to retinal cells in cell culture and in Myo7a-null mice. MYO7A cDNA, under control of a smCBA promoter, was packaged in single AAV2 and AAV5 vectors and as two overlapping halves in dual AAV2 vectors. The 7.9-kb smCBA-MYO7A exceeds the capacity of an AAV vector; packaging of such oversized constructs into single AAV vectors may involve fragmentation of the gene. Nevertheless, the AAV2 and AAV5 single vector preparations successfully transduced photoreceptor and retinal pigment epithelium cells, resulting in functional, full-length MYO7A protein and correction of mutant phenotypes, suggesting successful homologous recombination of gene fragments. With discrete, conventional-sized dual AAV2 vectors, full-length MYO7A was detected, but the level of protein expression was variable, and only a minority of cells showed phenotype correction. Our results show that MYO7A therapy with AAV2 or AAV5 single vectors is efficacious; however, the dual AAV2 approach proved to be less effective
Light hadron spectra and wave functions in quenched QCD with overlap quarks on a large lattice
A simulation of quenched QCD with the overlap Dirac operator has been
completed using 100 Wilson gauge configurations at beta=6 on an 18^3x64
lattice. We present results for meson and baryon masses, meson final state
"wave functions'' and other observables.Comment: 5 LaTeX pages (espcrc2.sty), 13 figures. Combined contributions by
J.H., L.L. and C.R. at Lattice2004(spectrum), Fermilab, June 21-26, 200
First results from a parametrized Fixed-Point QCD action
We have constructed a new fermion action which is an approximation to the
(chirally symmetric) Fixed-Point action, containing the full Clifford algebra
with couplings inside a hypercube and paths built from renormalization group
inspired fat links. We present an exploratory study of the light hadron
spectrum and the energy-momentum dispersion relation.Comment: Lattice2001(improvement), 3 pages, based on a talk by S.H; reference
update
Chiral measurements with the Fixed-Point Dirac operator and construction of chiral currents
In this preliminary study, we examine the chiral properties of the
parametrized Fixed-Point Dirac operator D^FP, see how to improve its chirality
via the Overlap construction, measure the renormalized quark condensate Sigma
and the topological susceptibility chi_t, and investigate local chirality of
near zero modes of the Dirac operator. We also give a general construction of
chiral currents and densities for chiral lattice actions.Comment: Lattice2001(chiral), based on a talk by T.J. and a poster by K.H., 6
page
Light hadron and diquark spectroscopy in quenched QCD with overlap quarks on a large lattice
A simulation of quenched QCD with the overlap Dirac operator has been
completed using 100 Wilson gauge configurations at beta = 6 on an 18^3 x 64
lattice and at beta = 5.85 on a 14^3 x 48 lattice, both in Landau gauge. We
present results for light meson and baryon masses, meson final state "wave
functions," and other observables, as well as some details on the numerical
techniques that were used. Our results indicate that scaling violations, if
any, are small. We also present an analysis of diquark correlations using the
quark propagators generated in our simulation.Comment: 28 LaTeX pages, 41 figures, v2: minor updates, version published in
JHE
The suitability of a seasonal ensemble hybrid framework including data-driven approaches for hydrological forecasting
Hydrological forecasts are important for operational water management and near-future planning, even more so in light of the increased occurrences of extreme events such as floods and droughts. Having a forecasting framework, which is flexible in terms of input forcings and forecasting locations (local, regional, or national) that can deliver this information in fast and computational efficient manner, is critical. In this study, the suitability of a hybrid forecasting framework, combining data-driven approaches and seasonal (re)forecasting information from dynamical models, to predict hydrological variables was explored. Target variables include discharge and surface water levels for various stations at a national scale, with the Netherlands as the focus. Five different machine learning (ML) models, ranging from simple to more complex and trained on historical observations of discharge, precipitation, evaporation, and seawater levels, were run with seasonal (re)forecast data, including the European Flood Awareness System (EFAS) and ECMWF seasonal forecast system (SEAS5), of these driver variables in a hindcast setting. The results were evaluated using the evaluation metrics, i.e. anomaly correlation coefficient (ACC), continuous ranked probability (skill) score (CRPS and CRPSS), and Brier skill score (BSS), in comparison to a climatological reference hindcast. Aggregating the results of all stations and ML models revealed that the hindcasting framework outperformed the climatological reference forecasts by roughly 60g% for discharge predictions (80g% for surface water level predictions). Skilful prediction for the first lead month, independently of the initialization month, can be made for discharge. The skill extends up to 2-3 months for spring months due to snowmelt dynamic captured in the training phase of the model. Surface water level hindcasts showed similar skill and skilful lead times. While the different ML models showed differences in performance during a testing and training phase using historical observations, running the ML framework in a hindcast setting showed only minor differences between the models, which is attributed to the uncertainty in seasonal forecasts. However, despite being trained on historical observations, the hybrid framework used in this study shows similar skilful predictions to previous large-scale forecasting systems. With our study, we show that a hybrid framework is able to bring location-specific skilful seasonal forecast information with global seasonal forecast inputs. At the same time, our hybrid approach is flexible and fast, and as such, a hybrid framework could be adapted to make it even more interesting to water managers and their needs, for instance, as part of a fast model-predictive control framework
Parabolic stable surfaces with constant mean curvature
We prove that if u is a bounded smooth function in the kernel of a
nonnegative Schrodinger operator on a parabolic Riemannian
manifold M, then u is either identically zero or it has no zeros on M, and the
linear space of such functions is 1-dimensional. We obtain consequences for
orientable, complete stable surfaces with constant mean curvature
in homogeneous spaces with four
dimensional isometry group. For instance, if M is an orientable, parabolic,
complete immersed surface with constant mean curvature H in
, then and if equality holds, then
M is either an entire graph or a vertical horocylinder.Comment: 15 pages, 1 figure. Minor changes have been incorporated (exchange
finite capacity by parabolicity, and simplify the proof of Theorem 1)
High-level real-time programming in Java
Real-time systems have reached a level of complexity beyond the scaling capability of the low-level or restricted languages traditionally used for real-time programming. While Metronome garbage collection has made it practical to use Java to implement real-time systems, many challenges remain for the construction of complex real-time systems, some specic to the use of Java and others simply due to the change in scale of such systems. The goal of our research is the creation of a comprehensive Java-based programming environment and methodology for the creation of complex real-time systems. Our goals include construction of a provably correct real-time garbage collec-tor capable of providing worst case latencies of 100 s, capa-ble of scaling from sensor nodes up to large multiprocessors; specialized programming constructs that retain the safety and simplicity of Java, and yet provide sub-microsecond la-tencies; the extension of Java's \write once, run anywhere" principle from functional correctness to timing behavior; on-line analysis and visualization that aids in the understanding of complex behaviors; and a principled probabilistic analy-sis methodology for bounding the behavior of the resulting systems. While much remains to be done, this paper describes the progress we have made towards these goals
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