21 research outputs found
Light-Quark FLIC Fermion Simulations of the Exotic Meson
We investigate the mass of the exotic meson, created with hybrid
interpolating fields. Access to light quark masses approaching 25 MeV is
facilitated by the use of the Fat-Link Irrelevant Clover (FLIC) fermion action,
and large () lattices. Our results indicate that the
exotic exhibits significant curvature close to the chiral limit, and yield a
mass in agreement with the candidate and exclusive of
the .Comment: 6 pages, 1 table, 2 figures, talk given at Lattice '05. Removed
unccessary figure
Pseudoscalar and vector meson form factors from lattice QCD
We present a study of the pseudoscalar and vector meson form factors,
calculated using the Fat-Link Irrelevant Clover (FLIC) action in the framework
of Quenched Lattice QCD. Of particular interest is the determination of a
negative quadrupole moment, indicating that the meson is not spherically
symmetric.Comment: 11 pages, 15 figures, 9 table
exotic meson at light quark masses
The mass of the exotic meson, created with hybrid interpolating
fields, is explored at light quark masses approaching 25 MeV (). Access to such light quark masses is facilitated by the use of
the Fat-Link Irrelevant Clover (FLIC) fermion action. Additionally, we make use
of large () lattices to obtain good control of statistical and
finite volume errors. Our results indicate that the exotic exhibits
significant curvature close the chiral limit, indicating previous linear
extrapolations, far from the chiral regime, have overestimated the mass of the
. We find for the first time in lattice studies a mass in
agreement with the candidate. We also find a strangeness 1
state with a mass close to 2 GeV.Comment: 8 pages, 11 figures, 3 tables, published versio
FLIC Fermions and Hadron Phenomenology
A pedagogical overview of the formulation of the Fat Link Irrelevant Clover
(FLIC) fermion action and its associated phenomenology is described. The
scaling analysis indicates FLIC fermions provide a new form of nonperturbative
O(a) improvement where near-continuum results are obtained at finite lattice
spacing. Spin-1/2 and spin-3/2, even and odd parity baryon resonances are
investigated in quenched QCD, where the nature of the Roper resonance and
Lambda(1405) are of particular interest. FLIC fermions allow efficient access
to the light quark-mass regime, where evidence of chiral nonanalytic behavior
in the Delta-baryon mass is observed.Comment: Invited plenary session talk at QNP 2002, International Conference on
Quark-Nuclear Physics, 9-14 June 2002, Forschungszentrum Julich, German
Excited Baryons in Lattice QCD
We present first results for the masses of positive and negative parity
excited baryons calculated in lattice QCD using an O(a^2)-improved gluon action
and a fat-link irrelevant clover (FLIC) fermion action in which only the
irrelevant operators are constructed with APE-smeared links. The results are in
agreement with earlier calculations of N^* resonances using improved actions
and exhibit a clear mass splitting between the nucleon and its chiral partner.
An correlation matrix analysis reveals two low-lying J^P=(1/2)^- states with a
small mass splitting. The study of different Lambda interpolating fields
suggests a similar splitting between the lowest two Lambda1/2^- octet states.
However, the empirical mass suppression of the Lambda^*(1405) is not evident in
these quenched QCD simulations, suggesting a potentially important role for the
meson cloud of the Lambda^*(1405) and/or a need for more exotic interpolating
fields.Comment: Correlation matrix analysis performed. Increased to 400
configurations. 22 pages, 13 figures, 15 table
ABCA transporter gene expression and poor outcome in epithelial ovarian cancer
Background ATP-binding cassette (ABC) transporters play various roles in cancer biology and drug resistance, but their association with outcomes in serous epithelial ovarian cancer (EOC) is unknown. Methods The relationship between clinical outcomes and ABC transporter gene expression in two independent cohorts of high-grade serous EOC tumors was assessed with real-time quantitative polymerase chain reaction, analysis of expression microarray data, and immunohistochemistry. Associations between clinical outcomes and ABCA transporter gene single nucleotide polymorphisms were tested in a genome-wide association study. Impact of short interfering RNA-mediated gene suppression was determined by colony forming and migration assays. Association with survival was assessed with Kaplan-Meier analysis and log-rank tests. All statistical tests were two-sided. Results Associations with outcome were observed with ABC transporters of the A subfamily, but not with multidrug transporters. High-level expression of ABCA1, ABCA6, ABCA8, and ABCA9 in primary tumors was statistically significantly associated with reduced survival in serous ovarian cancer patients. Low levels of ABCA5 and the C-allele of rs536009 were associated with shorter overall survival (hazard ratio for death = 1.50; 95% confidence interval [CI] =1.26 to 1.79; P = 6.5e-6). The combined expression pattern of ABCA1, ABCA5, and either ABCA8 or ABCA9 was associated with particularly poor outcome (mean overall survival in group with adverse ABCA1, ABCA5 and ABCA9 gene expression = 33.2 months, 95% CI = 26.4 to 40.1; vs 55.3 months in the group with favorable ABCA gene expression, 95% CI = 49.8 to 60.8; P =. 001), independently of tumor stage or surgical debulking status. Suppression of cholesterol transporter ABCA1 inhibited ovarian cancer cell growth and migration in vitro, and statin treatment reduced ovarian cancer cell migration. Conclusions Expression of ABCA transporters was associated with poor outcome in serous ovarian cancer, implicating lipid trafficking as a potentially important process in EOC. © 2014 The Author 2014. Published by Oxford University Press. All rights reserved
Genome-wide association studies of cancer: current insights and future perspectives.
Genome-wide association studies (GWAS) provide an agnostic approach for investigating the genetic basis of complex diseases. In oncology, GWAS of nearly all common malignancies have been performed, and over 450 genetic variants associated with increased risks have been identified. As well as revealing novel pathways important in carcinogenesis, these studies have shown that common genetic variation contributes substantially to the heritable risk of many common cancers. The clinical application of GWAS is starting to provide opportunities for drug discovery and repositioning as well as for cancer prevention. However, deciphering the functional and biological basis of associations is challenging and is in part a barrier to fully unlocking the potential of GWAS