10,005 research outputs found

    Improved Ways to Compare Simulations to Data

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    Theoretical models for structure formation with Gaussian initial fluctuations have been worked out in considerable detail and compared with observations on various scales. It is on nonlinear scales \lsim 10 \ h^{-1}\ {\rm Mpc} that the greatest differences exist between Ω=1\Omega=1 models that have been normalized to agree on the largest scales with the COBE data; here especially there is a need for better statistical tests which are simultaneously {\it robust}, {\it discriminatory}, and {\it interpretable}. The era at which galaxy and cluster formation occurs is also a critical test of some models. Needs for the future include faster and cleverer codes, better control of cosmic variance in simulations, better understanding of processes leading to galaxy formation, better ways of comparing observational data with models, and better access to observational and simulation data.Comment: 9 pages, self-extracting uuencoded postscript, encoded with uufile

    Citywide Transportation Greenhouse Gas Emissions Inventories: A Review of Selected Methodologies

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    Outlines the methodological issues in creating transportation emissions inventories and how they affect the results, reviews currently used methodologies, and explores ways to integrate inventories with climate policies to inform reduction strategies

    The Relationship of the Clinical Disc Margin and Bruch's Membrane Opening in Normal and Glaucoma Subjects.

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    PurposeWe tested the hypotheses that the mismatch between the clinical disc margin (CDM) and Bruch's membrane opening (BMO) is a function of BMO area (BMOA) and is affected by the presence of glaucoma.MethodsA total of 45 normal eyes (45 subjects) and 53 glaucomatous eyes (53 patients) were enrolled and underwent radial optic nerve head (ONH) imaging with spectral domain optical coherence tomography. The inner tip of the Bruch's membrane (BM) and the clinical disc margin were marked on radial scans and optic disc photographs, and were coregistered with custom software. The main outcome measure was the difference between the clinical disc area (CDA) and BMOA, or CDA-BMOA mismatch, as a function of BMOA and diagnosis. Multivariate regression analyses were used to explore the influence of glaucoma and BMOA on the mismatch.ResultsGlobal CDA was larger than BMOA in both groups but the difference was statistically significant only in the normal group (1.98 ± 0.37 vs. 1.85 ± 0.45 mm2, P = 0.02 in the normal group; 1.96 ± 0.38 vs. 1.89 ± 0.56 mm2, P = 0.08 in the glaucoma group). The sectoral CDA-BMOA mismatch was smaller in superotemporal (P = 0.04) and superonasal (P = 0.05) sectors in the glaucoma group. The normalized CDA-BMOA difference decreased with increasing BMOA in both groups (P < 0.001). Presence or severity of glaucoma did not affect the CDA-BMOA difference (P > 0.14).ConclusionsClinical disc area was larger than BMOA in normal and glaucoma eyes but reached statistical significance only in the former group. The CDA-BMOA mismatch diminished with increasing BMOA but was not affected by presence of glaucoma. These findings have important clinical implications regarding clinical evaluation of the ONH

    Massive Milky Way Satellites in Cold and Warm Dark Matter: Dependence on Cosmology

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    We investigate the claim that the largest subhaloes in high resolution dissipationless cold dark matter (CDM) simulations of the Milky Way are dynamically inconsistent with observations of its most luminous satellites. We find that the inconsistency is largely attributable to the large values of \sigma_8 and n_s adopted in the discrepant simulations producing satellites that form too early and therefore are too dense. We find the tension between observations and simulations adopting parameters consistent with WMAP9 is greatly diminished making the satellites a sensitive test of CDM. We find the Via Lactea II halo to be atypical for haloes in a WMAP3 cosmology, a discrepancy that we attribute to its earlier formation epoch than the mean for its mass. We also explore warm dark matter (WDM) cosmologies for 1--4 keV thermal relics. In 1 keV cosmologies subhaloes have circular velocities at kpc scales ~ 60% lower than their CDM counterparts, but are reduced by only 10% in 4 keV cosmologies. Since relic masses < 2-3 keV are ruled out by constraints from the number of Milky Way satellites and Lyman-\alpha\ forest, WDM has a minor effect in reducing the densities of massive satellites. Given the uncertainties on the mass and formation epoch of the Milky Way, the need for reducing the satellite densities with baryonic effects or WDM is alleviated.Comment: 11 pages, 7 figures, submitted to MNRA

    Sustainability Standards and Stakeholder Engagement: Lessons From Carbon Markets

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    Stakeholders play an increasingly active role in private governance, including development of standards for measuring sustainability. Building on prior studies focused on standards and stakeholder engagement, we use an innovation management theoretical lens to compare stakeholder engagement and standards developed in two carbon markets: the Climate Action Reserve and the U.N.’s Clean Development Mechanism. We develop and test hypotheses regarding how different processes of stakeholder engagement in standard development affect the number, identity, and age of stakeholders involved, as well as the variation and quality of the resulting standards. In doing so, we contribute to the growing literature on stakeholder engagement in developing sustainability standards

    The X-Ray Concentration-Virial Mass Relation

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    We present the concentration (c)-virial mass (M) relation of 39 galaxy systems ranging in mass from individual early-type galaxies up to the most massive galaxy clusters, (0.06-20) x 10^{14} M_sun. We selected for analysis the most relaxed systems possessing the highest quality data currently available in the Chandra and XMM public data archives. A power-law model fitted to the X-ray c-M relation requires at high significance (6.6 sigma) that c decreases with increasing M, which is a general feature of CDM models. The median and scatter of the c-M relation produced by the flat, concordance LCDM model (Omega_m=0.3, sigma_8=0.9) agrees with the X-ray data provided the sample is comprised of the most relaxed, early forming systems, which is consistent with our selection criteria. Holding the rest of the cosmological parameters fixed to those in the concordance model the c-M relation requires 0.76< sigma_8 <1.07 (99% conf.), assuming a 10% upward bias in the concentrations for early forming systems. The tilted, low-sigma_8 model suggested by a new WMAP analysis is rejected at 99.99% confidence, but a model with the same tilt and normalization can be reconciled with the X-ray data by increasing the dark energy equation of state parameter to w ~ -0.8. When imposing the additional constraint of the tight relation between sigma_8 and Omega_m from studies of cluster abundances, the X-ray c-M relation excludes (>99% conf.) both open CDM models and flat CDM models with Omega_m ~1. This result provides novel evidence for a flat, low-Omega_m universe with dark energy using observations only in the local (z << 1) universe. Possible systematic errors in the X-ray mass measurements of a magnitude ~10% suggested by CDM simulations do not change our conclusions.Comment: Accepted for Publication in ApJ; 13 pages, 4 figures; minor clarifications and updates; correlation coefficients corrected in Table 1 (correct values were used in the analysis in previous versions); conclusions unchange

    Constraints on decaying Dark Matter from XMM-Newton observations of M31

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    We derive constraints on parameters of the radiatively decaying Dark Matter (DM) particles, using XMM-Newton EPIC spectra of the Andromeda galaxy (M31). Using the observations of the outer (5'-13') parts of M31 we improve the existing constraints. For the case of sterile neutrino DM, combining our constraints with the latest computation of abundances of sterile neutrino in the Dodelson-Widrow (DW) scenario, we obtain the lower mass limit m_s < 4 keV, which is stronger than the previous one m_s < 6 kev, obtained recently by Asaka et al. (2007) [hep-ph/0612182]. Comparing this limit with the most recent results on Lyman-alpha forest analysis of Viel et al. (2007) [arXiv:0709.0131] (m_s > 5.6 kev), we argue that the scenario in which all the DM is produced via DW mechanism is ruled out. We discuss however other production mechanisms and note that the sterile neutrino remains a viable candidate of Dark Matter, either warm or cold.Comment: 13 pages, 12 figure

    ORTHOGONALITY OF STRUCTURED DERIVED ENTITIES

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    Structured entities, derivative entities and their order are presented. The orthogonality metric for structured and derivative entities is build. This metric is implemented. The sets of structured entities and first order derivative entities will be evaluated and analyzed.structured entities, derivative entities, metric, sets.
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