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Decoding the spectra of SDSS early-type galaxies: new indicators of age and recent star formation
Rogers, Ben,Ferreras, Ignacio,Lahav, Ofer,Bernardi, Mariangela,Kaviraj, Sugata,Yi, Sukyoung K. Blackwell Publishing Ltd 2007 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.382 No.2
<P>ABSTRACT</P><P>We apply principal component analysis (PCA) to a sample of early-type galaxies from the Sloan Digital Sky Survey (SDSS) in order to infer differences in their star formation histories from their unresolved stellar populations. We select a <I>z</I> < 0.1 volume-limited sample comprising ∼7000 early-type galaxies from SDSS/Data Release 4. Out of the first few principal components (PC), we study four which give information about stellar populations and velocity dispersion. We construct two parameters (η and ζ) as linear combinations of PC1 and PC2. The four components can be presented as ‘optimal filters’ to explore in detail the properties of the underlying stellar populations. By comparing various photospectroscopic observables – including near-ultraviolet (NUV) photometry from Galaxy Evolution Explorer (GALEX) – we find ζ to be most sensitive to recent episodes of star formation, and η to be strongly dependent on the average age of the stellar populations. Both η and ζ also depend on metallicity. We apply these optimal filters to composite spectra assembled by Bernardi et al. The distribution of the η component of the composites appear to be indistinguishable between high- and low-density regions, whereas the distribution of ζ parameters have a significant skew towards lower values for galaxies in low-density regions. This result suggests that galaxies in lower density environments are less likely to present weak episodes of recent star formation. In contrast, a significant number of galaxies from our high-density subsample – which includes clusters (both outer regions and centres) and groups – underwent small but detectable recent star formation at high metallicity, in agreement with recent estimates targeting elliptical galaxies in Hickson Compact Groups and in the field.</P>
Milne, Roger L.,Bení,tez, Javier,Nevanlinna, Heli,Heikkinen, Tuomas,Aittomä,ki, Kristiina,Blomqvist, Carl,Arias, José,Ignacio,Zamora, M. Pilar,Burwinkel, Barbara,Bartram, Claus R.,Mein Oxford University Press 2009 Journal of the National Cancer Institute Vol.101 No.14
<P>BACKGROUND: A recent genome-wide association study identified single-nucleotide polymorphism (SNP) 2q35-rs13387042 as a marker of susceptibility to estrogen receptor (ER)-positive breast cancer. We attempted to confirm this association using the Breast Cancer Association Consortium. METHODS: 2q35-rs13387042 SNP was genotyped for 31 510 women with invasive breast cancer, 1101 women with ductal carcinoma in situ, and 35 969 female control subjects from 25 studies. Odds ratios (ORs) were estimated by logistic regression, adjusted for study. Heterogeneity in odds ratios by each of age, ethnicity, and study was assessed by fitting interaction terms. Heterogeneity by each of invasiveness, family history, bilaterality, and hormone receptor status was assessed by subclassifying case patients and applying polytomous logistic regression. All statistical tests were two-sided. RESULTS: We found strong evidence of association between rs13387042 and breast cancer in white women of European origin (per-allele OR = 1.12, 95% confidence interval [CI] = 1.09 to 1.15; P(trend) = 1.0 x 10(-19)). The odds ratio was lower than that previously reported (P = .02) and did not vary by age or ethnicity (all P > or = .2). However, it was higher when the analysis was restricted to case patients who were selected for a strong family history (P = .02). An association was observed for both ER-positive (OR = 1.14, 95% CI = 1.10 to 1.17; P = 10(-15)) and ER-negative disease (OR = 1.10, 95% CI = 1.04 to 1.15; P = .0003) and both progesterone receptor (PR)-positive (OR = 1.15, 95% CI = 1.11 to 1.19; P = 5 x 10(-14)) and PR-negative disease (OR = 1.10, 95% CI = 1.06 to 1.15; P = .00002). CONCLUSION: The rs13387042 is associated with both ER-positive and ER-negative breast cancer in European women.</P>
A Study to Optimize a Commerical Vehicle Fuel Consumption Using Vehicle Simulation
Myungseok Lyu,Steven Whelan,Ben Rogers 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_1
An approach to optimizing vehicle fuel economy is described based on a study of a commercial vehicle. The approach is based on using a V-SIM software vehicle simulation to identify the relative efficiency of each of the vehicle systems, such as the engine hardware, engine software calibration, transmission, cooling system and ancillary drives. The simulation based approach offers a detailed understanding of what vehicle systems are underperforming and by how much the vehicle fuel economy can be improved if those systems are brought up to best-in-class performance. In this way, the optimum vehicle fuel economy can be provided to the vehicle customer. A further benefit is that the simulation requires only a minimum of vehicle testing for initial validation, with all subsequent field test cycles performed in software, thereby reducing development time and cost for the manufacturer.