265 research outputs found
How to compute Green's Functions for entire Mass Trajectories within Krylov Solvers
The availability of efficient Krylov subspace solvers play a vital role for
the solution of a variety of numerical problems in computational science. Here
we consider lattice field theory. We present a new general numerical method to
compute many Green's functions for complex non-singular matrices within one
iteration process. Our procedure applies to matrices of structure , with
proportional to the unit matrix, and can be integrated within any Krylov
subspace solver. We can compute the derivatives of the solution
vector with respect to the parameter and construct the Taylor expansion
of around . We demonstrate the advantages of our method using a minimal
residual solver. Here the procedure requires intermediate vector for each
Green's function to compute. As real life example, we determine a mass
trajectory of the Wilson fermion matrix for lattice QCD. Here we find that we
can obtain Green's functions at all masses at the price of one
inversion at mass .Comment: 11 pages, 2 eps-figures, needs epsf.st
A Parallel SSOR Preconditioner for Lattice QCD
A parallelizable SSOR preconditioning scheme for Krylov subspace iterative
solvers in lattice QCD applications involving Wilson fermions is presented. In
actual Hybrid Monte Carlo and quark propagator calculations it helps to reduce
the number of iterations by a factor of 2 compared to conventional odd-even
preconditioning. This corresponds to a gain in cpu-time of 30\% - 70\% over
odd-even preconditioning.Comment: Talk presented at LATTICE96(algorithms), 3 pages, LaTeX file, 3
epsf-files include
SESAM and TXL Results for Wilson Action--A Status Report
Results from two studies of full QCD with two flavours of dynamical Wilson
fermions are presented. At beta=5.6, the region 0.83 > m_pi/m_rho > 0.56 at
m_pia > 0.23 L^{-1} is explored. The SESAM collaboration has generated
ensembles of about 200 statistically independent configurations on a 16^3 x
32-lattice at three different kappa-values and is entering the final phase of
data analysis. The TXL simulation on a 24^3 x 40-lattice at two kappa-values
has reached half statistics and data analysis has started recently, hence most
results presented here are preliminary. The focus of this report is fourfold:
we demonstrate that algorithmic improvements like fast Krylov solvers and
parallel preconditioning recently introduced can be put into practise in full
QCD simulations, we present encouraging observations as to the critical
dynamics of the Hybrid Monte Carlo algorithm in the approach to the chiral
limit, we mention signal improvements of noisy estimator techniques for
disconnected diagrams to the pi-N sigma term, and we report on SESAM's results
for light hadron spectrum, light quark masses, and heavy quarkonia.Comment: 24 pages, tex + postscript figures, to appear in Proceedings of Int.
Workshop "Lattice QCD on Parallel Computers", University of Tsukuba, Japa
Critical Dynamics of the Hybrid Monte Carlo Algorithm
We investigate the critical dynamics of the Hybrid Monte Carlo algorithm
approaching the chiral limit of standard Wilson fermions. Our observations are
based on time series of lengths O(5000) for a variety of observables. The
lattice sizes are 16^3 x 32 and 24^3 x 40. We work at beta=5.6, and
kappa=0.156, 0.157, 0.1575, 0.158, with 0.83 > m_pi/m_rho > 0.55. We find
surprisingly small integrated autocorrelation times for local and extended
observables. The dynamical critical exponent of the exponential
autocorrelation time is compatible with 2. We estimate the total computational
effort to scale between V^2 and V^2.25 towards the chiral limit.Comment: 3 pages, Latex with espcrc2.sty and postscript figures, Talk given at
Lattice 9
Antisense repression of the chloroplast triose phosphate translocator affects carbon partitioning in transgenic potato plants.
GPU-Accelerated Asynchronous Error Correction for Mixed Precision Iterative Refinement
In hardware-aware high performance computing, block-asynchronous iteration and mixed precision iterative refinement are two techniques that may be used to leverage the computing power of SIMD accelerators like GPUs in the iterative solution of linear equation systems. although they use a very different approach for this purpose, they share the basic idea of compensating the convergence properties of an inferior numerical algorithm by a more efficient usage of the provided computing power. In this paper, we analyze the potential of combining both techniques. Therefore, we derive a mixed precision iterative refinement algorithm using a block-asynchronous iteration as an error correction solver, and compare its performance with a pure implementation of a block-asynchronous iteration and an iterative refinement method using double precision for the error correction solver. For matrices from the University of Florida Matrix collection, we report the convergence behaviour and provide the total solver runtime using different GPU architectures
Moments of Nucleon Light Cone Quark Distributions Calculated in Full Lattice QCD
Moments of the quark density, helicity, and transversity distributions are
calculated in unquenched lattice QCD. Calculations of proton matrix elements of
operators corresponding to these moments through the operator product expansion
have been performed on lattices for Wilson fermions at using configurations from the SESAM collaboration and at
using configurations from SCRI. One-loop perturbative renormalization
corrections are included. At quark masses accessible in present calculations,
there is no statistically significant difference between quenched and full QCD
results, indicating that the contributions of quark-antiquark excitations from
the Dirac Sea are small. Close agreement between calculations with cooled
configurations containing essentially only instantons and the full gluon
configurations indicates that quark zero modes associated with instantons play
a dominant role. Naive linear extrapolation of the full QCD calculation to the
physical pion mass yields results inconsistent with experiment. Extrapolation
to the chiral limit including the physics of the pion cloud can resolve this
discrepancy and the requirements for a definitive chiral extrapolation are
described.Comment: 53 Pages Revtex, 26 Figures, 9 Tables. Added additional reference and
updated referenced data in Table I
Papillary carcinoma of the thyroid: methylation is not involved in the regulation of MET expression
Hypomethylation has been reported to be responsible for the activation of several oncogenes. The possibility that hypomethylation is involved in the regulation of MET transcription was investigated through the analysis of the methylation status of one CpG island containing 43 CpGs in six cases of papillary carcinoma, in the corresponding normal thyroid tissue, and in two cases of hyperplastic goitre. Evidence of methylation was not found in any of the analysed CpG. © 2004 Cancer Research UK
Influence of extracellular rnas, released by rheumatoid arthritis synovial fibroblasts, on their adhesive and invasive properties
© 2016 by The American Association of Immunologists, Inc.Extracellular RNA (exRNA) has been characterized as a molecular alarm signal upon cellular stress or tissue injury and to exert biological functions as a proinflammatory, prothrombotic, and vessel permeability-regulating factor. In this study, we investigated the contribution of exRNA and its antagonist RNase1 in a chronic inflammatory joint disease, rheumatoid arthritis (RA). Upon immunohistochemical inspection of RA, osteoarthritis (OA), and psoriatic arthritis synovium, exRNA was detectable only in the RA synovial lining layer, whereas extracellular DNAwas detectable in various areas of synovial tissue. In vitro, exRNA (150-5000 nt) was released by RA synovial fibroblasts (RASF) under hypoxic conditions but not under normoxia or TNF-A treatment. RNase activity was increased in synovial fluid from RA and OA patients compared with psoriatic arthritis patients, whereas RNase activity of RASF and OASF cultures was not altered by hypoxia. Reduction of exRNA by RNase1 treatment decreased adhesion of RASF to cartilage, but it had no influence on their cell proliferation or adhesion to endothelial cells. In vivo, treatment with RNase1 reduced RASF invasion into coimplanted cartilage in the SCID mouse model of RA. We also analyzed the expression of neuropilins in synovial tissue and SF, as they may interact with vascular endothelial growth factor signaling and exRNA. The data support the concepts that the exRNA/RNase1 system participates in RA pathophysiology and that RASF are influenced by exRNA in a prodestructive manner. The Journal of Immunology, 2016, 197: 2589-2597
Long-term efficacy, tolerability and overall survival in patients with platinum-sensitive, recurrent high-grade serous ovarian cancer treated with maintenance olaparib capsules following response to chemotherapy
BACKGROUND: In Study 19, maintenance monotherapy with olaparib significantly prolonged progression-free survival vs placebo in patients with platinum-sensitive, recurrent high-grade serous ovarian cancer. METHODS: Study 19 was a randomised, placebo-controlled, Phase II trial enrolling 265 patients who had received at least two platinum-based chemotherapy regimens and were in complete or partial response to their most recent regimen. Patients were randomised to olaparib (capsules; 400âmg bid) or placebo. We present long-term safety and final mature overall survival (OS; 79% maturity) data, from the last data cut-off (9 May 2016). RESULTS: Thirty-two patients (24%) received maintenance olaparib for over 2 years; 15 (11%) did so for over 6 years. No new tolerability signals were identified with long-term treatment and adverse events were generally low grade. The incidence of discontinuations due to adverse events was low (6%). An apparent OS advantage was observed with olaparib vs placebo (hazard ratio 0.73, 95% confidence interval 0.55â0.95, Pâ=â0.02138) irrespective of BRCA1/2 mutation status, although the predefined threshold for statistical significance was not met. CONCLUSIONS: Study 19 showed a favourable final OS result irrespective of BRCA1/2 mutation status and unprecedented long-term benefit with maintenance olaparib for a subset of platinum-sensitive, recurrent ovarian cancer patients
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