500 research outputs found
NRQCD and Static Systems -- A General Variational Approach
We present initial results from Monte Carlo simulations of NRQCD-light,
static-light, and NRQCD-NRQCD mesons, using a variational technique (MOST), as
part of our ongoing calculation of the decay constant. The basis states
for the variational calculation are quark-antiquark operators separated by all
possible relative distances not equivalent under the cubic group (for example,
for a lattice there are 286 operators). The efficacy of the method is
demonstrated by the good plateaus obtained for the ground state and the clean
extraction of the wave functions of the ground and first radially excited
state.Comment: Contribution to the Lattice '94 conference, 3 pages,
uuencoded-compressed PostScript fil
Rare and Common Genetic Variants, Smoking, and Body Mass Index: Progression and Earlier Age of Developing Advanced Age-Related Macular Degeneration
Purpose: To determine behavioral and genetic factors associated with incidence and age of progression to advanced age-related macular degeneration (AMD), geographic atrophy (GA), and neovascular disease (NV), and to quantify these effects.
Methods: Longitudinal analyses were conducted among 5421 eyes with nonadvanced AMD at baseline in 2976 participants in the Age-Related Eye Disease Study (mean age of 68.8 (+/-5.0), 56.1% female). Progression was confirmed based on two consecutive visits on the AMD severity scale. Separate analyses for progression and age of progression were performed. All analyses adjusted for correlation between eyes, demographic and behavioral covariates, baseline severity scale, and genetic variants.
Results: A higher genetic risk score (GRS) including eight genetic variants was associated with a higher rate of progression to advanced AMD within each baseline severity scale, especially for the highest risk intermediate level AMD category, and smoking further increased this risk. When assessing age when progression to advanced disease occurred, smoking reduced age of onset by 3.9 years (P \u3c 0.001), and higher body mass index (BMI) led to earlier onset by 1.7 years (P = 0.003), with similar results for GA and NV. Genetic variants associated with earlier age of progression were CFH R1201C (4.3 years), C3 K155Q (2.15 years), and ARMS2/HTRA1 (0.8 years per allele).
Conclusions: Rare variants in the complement pathway and a common risk allele in ARMS2/HTRA1, smoking, and higher BMI can lead to as much as 11.5 additional years of disease and treatment burden. Closer adherence to healthy lifestyles could reduce years of visual impairment
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Three New Genetic Loci (R1210C in CFH, Variants in COL8A1 and RAD51B) Are Independently Related to Progression to Advanced Macular Degeneration
Objectives: To assess the independent impact of new genetic variants on conversion to advanced stages of AMD, controlling for established risk factors, and to determine the contribution of genes in predictive models. Methods: In this prospective longitudinal study of 2765 individuals, 777 subjects progressed to neovascular disease (NV) or geographic atrophy (GA) in either eye over 12 years. Recently reported genetic loci were assessed for their independent effects on incident advanced AMD after controlling for 6 established loci in 5 genes, and demographic, behavioral, and macular characteristics. New variants which remained significantly related to progression were then added to a final multivariate model to assess their independent effects. The contribution of genes to risk models was assessed using reclassification tables by determining risk within cross-classified quintiles for alternative models. Results: Three new genetic variants were significantly related to progression: rare variant R1210C in CFH (hazard ratio (HR) 2.5, 95% confidence interval [CI] 1.2–5.3, P = 0.01), and common variants in genes COL8A1 (HR 2.0, 95% CI 1.1–3.5, P = 0.02) and RAD51B (HR 0.8, 95% CI 0.60–0.97, P = 0.03). The area under the curve statistic (AUC) was significantly higher for the 9 gene model (.884) vs the 0 gene model (.873), P = .01. AUC’s for the 9 vs 6 gene models were not significantly different, but reclassification analyses indicated significant added information for more genes, with adjusted odds ratios (OR) for progression within 5 years per one quintile increase in risk score of 2.7, P<0.001 for the 9 vs 6 loci model, and OR 3.5, P<0.001 for the 9 vs. 0 gene model. Similar results were seen for NV and GA. Conclusions: Rare variant CFH R1210C and common variants in COL8A1 and RAD51B plus six genes in previous models contribute additional predictive information for advanced AMD beyond macular and behavioral phenotypes
Semileptonic Decays: an Update Down Under
Heavy-meson semileptonic decays calculations on the lattice are reviewed. The
focus is upon obtaining reliable matrix elements. Errors that depend upon the
lattice spacing, , are an important source of systematic error. Full
improvement of matrix elements for arbitrary-mass four-component quarks is
discussed. With improvement, bottom-quark matrix elements can be calculated
directly using current lattices. Momentum dependent errors for -improved
quarks and statistical noise limit momenta to around 1 GeV/c with current
lattices. Hence, maximum recoil momenta can be reached for decays while
only a fraction of the maximum recoil momentum can be reliably studied for the
light-meson decay modes of the . Differential decay rates and partial widths
are phenomenologically important quantities in decays that can be reliably
determined with present lattices.Comment: 14 pages, 9 postscript figures, requires espcrc2.st
Analytical method for detecting outlier evaluators
Epidemiologic and medical studies often rely on evaluators to obtain
measurements of exposures or outcomes for study participants, and valid
estimates of associations depends on the quality of data. Even though
statistical methods have been proposed to adjust for measurement errors, they
often rely on unverifiable assumptions and could lead to biased estimates if
those assumptions are violated. Therefore, methods for detecting potential
`outlier' evaluators are needed to improve data quality during data collection
stage. In this paper, we propose a two-stage algorithm to detect `outlier'
evaluators whose evaluation results tend to be higher or lower than their
counterparts. In the first stage, evaluators' effects are obtained by fitting a
regression model. In the second stage, hypothesis tests are performed to detect
`outlier' evaluators, where we consider both the power of each hypothesis test
and the false discovery rate (FDR) among all tests. We conduct an extensive
simulation study to evaluate the proposed method, and illustrate the method by
detecting potential `outlier' audiologists in the data collection stage for the
Audiology Assessment Arm of the Conservation of Hearing Study, an epidemiologic
study for examining risk factors of hearing loss in the Nurses' Health Study
II. Our simulation study shows that our method not only can detect true
`outlier' evaluators, but also is less likely to falsely reject true `normal'
evaluators. Our two-stage `outlier' detection algorithm is a flexible approach
that can effectively detect `outlier' evaluators, and thus data quality can be
improved during data collection stage
Enhancement of the decay rate
The enhancement of the decay rate due
to four-fermion processes of weak scattering and Pauli interference is
calculated within the quark model. An estimate of the relative wave
function at zero separation, , is obtained in terms of the
hyperfine splitting, the hyperfine splitting,
and the meson decay constant . For MeV, MeV, and MeV, we find
ps, to be compared with
the observed enhancement
ps. Even such a meager enhancement entails a value of
considerably larger than the corresponding value of in the
baryon.Comment: 7 pages, latex, no figure
Food Predictors of Plasma Carotenoids
Empirical prediction models that weight food frequency questionnaire (FFQ) food items by their relation to nutrient biomarker concentrations may estimate nutrient exposure better than nutrient intakes derived from food composition databases. Carotenoids may especially benefit because contributing foods vary in bioavailability and assessment validity. Our objective was to develop empirical prediction models for the major plasma carotenoids and total carotenoids and evaluate their validity compared with dietary intakes calculated from standard food composition tables. 4180 nonsmoking women in the Nurses’ Health Study (NHS) blood subcohort with previously measured plasma carotenoids were randomly divided into training (n = 2787) and testing (n = 1393) subsets. Empirical prediction models were developed in the training subset by stepwise selection from foods contributing ≥0.5% to intake of the relevant carotenoid. Spearman correlations between predicted and measured plasma concentrations were compared to Spearman correlations between dietary intake and measured plasma concentrations for each carotenoid. Three to 12 foods were selected for the α-carotene, β-carotene, β-cryptoxanthin, lutein/zeaxanthin, lycopene, and total carotenoids prediction models. In the testing subset, Spearman correlations with measured plasma concentrations for the calculated dietary intakes and predicted plasma concentrations, respectively, were 0.31 and 0.37 for α-carotene, 0.29 and 0.31 for β-carotene, 0.36 and 0.41 for β-cryptoxanthin, 0.28 and 0.31 for lutein/zeaxanthin, 0.22 and 0.23 for lycopene, and 0.22 and 0.27 for total carotenoids. Empirical prediction models may modestly improve assessment of some carotenoids, particularly α-carotene and β-cryptoxanthin
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