1,512 research outputs found

    How well do U.S. western water markets convey economic information

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    A magnified view of star formation at redshift 0.9 from two lensed galaxies

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    We present new narrow-band H alpha imaging from the Hubble Space Telescope of two redshift 0.91 galaxies that have been lensed by foreground galaxy cluster Abell 2390. These data probe spatial scales as small as 0.3 kpc, providing a magnified look at the morphology of star formation at an epoch when the global star formation rate was high. However, dust attenuates our spatially resolved star formation rate (SFR) indicators, the H alpha and rest-UV emission, and we lack a direct measurement of extinction. Other studies have found that ionized gas in galaxies tends to be roughly 50 percent more obscured than stars; however, given an unextincted measurement of the SFR we can quantify the relative stellar to nebular extinction and the extinction in H{\alpha}. We infer SFRs from Spitzer and Herschel mid- to far-infrared observations and compare these to integrated H alpha and rest-UV SFRs; this yields stellar to nebular extinction ratios consistent with previous studies. We take advantage of high spatial resolution and contextualize these results in terms of the source-plane morphologies, comparing the distribution of H alpha to that of the rest-frame UV and optical light. In one galaxy, we measure separate SFRs in visually distinct clumps, but can set only a lower limit on the extinction and thus the star formation. Consequently, the data are also consistent with there being an equal amount of extinction along the lines of sight to the ionized gas as to the stars. Future observations in the far-infrared could settle this by mapping out the dust directly.Comment: Published as 2014, The Astronomical Journal, 148, 6

    The origin and function of self-incompatibility in flowering plants

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    The evolutionary significance of self-incompatibility (SI) traditionally has been linked to reduced inbreeding through enforced outcrossing. This view is founded on the premise that outcrossing reduces inbreeding. It is important, when considering the evolutionary significance of any genetic system, to try to distinguish those factors related to the evolution of, from those related to the maintenance of, the system in question. Three factors are considered important for the maintenance of SI: (1) phylogenetic constraint in species descended from SI ancestors, (2) reduced inbreeding in populations, and (3) fitness benefits to individuals resulting from the avoidance of selfing. I suggest that the first two factors should be rejected when considering the origin of SI (whether one or more origins are hypothesized) and that the increase in individual fitness resulting from the avoidance of self-fertilization among individuals that are heterozygous for deleterious alleles may be sufficient to account for the origin of SI. Self-fertilization in plants (except in species that predominantly self-fertilize) generally results in a reduction in fitness of some individuals due to the increased expression of deleterious or lethal recessive alleles, regardless of the degree of inbreeding in the population or the frequency of the allele in question. Inbreeding is a consequence of population structure in many outcrossing plant species. Complex (multi-locus and multi-allelic) systems of SI exist that reduce inbreeding. However, it is argued that these are derived either from simpler systems of SI that may have very little or no effect on inbreeding, in which case any effect on level of inbreeding is secondary, or are not true self-incompatibility systems and are part of a regulatory system that serves to balance the level of inbreeding and outbreeding. Multi-locus and multi-allelic systems of SI and heteromorphic systems of SI are discussed in terms of derived versus ancestral characteristics. A reassessment of the role of breeding systems in the development of a population structure promoting inbreeding is suggested, which may have been of crucial importance in the success and diversification of angiosperms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47845/1/497_2004_Article_BF00192758.pd

    The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: RSD measurement from the power spectrum and bispectrum of the DR12 BOSS galaxies

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    We measure and analyse the bispectrum of the final, Data Release 12, galaxy sample provided by the Baryon Oscillation Spectroscopic Survey, splitting by selection algorithm into LOWZ and CMASS galaxies. The LOWZ sample contains 361\,762 galaxies with an effective redshift of zLOWZ=0.32z_{\rm LOWZ}=0.32, and the CMASS sample 777\,202 galaxies with an effective redshift of zCMASS=0.57z_{\rm CMASS}=0.57. Combining the power spectrum, measured relative to the line-of-sight, with the spherically averaged bispectrum, we are able to constrain the product of the growth of structure parameter, ff, and the amplitude of dark matter density fluctuations, σ8\sigma_8, along with the geometric Alcock-Paczynski parameters, the product of the Hubble constant and the comoving sound horizon at the baryon drag epoch, H(z)rs(zd)H(z)r_s(z_d), and the angular distance parameter divided by the sound horizon, DA(z)/rs(zd)D_A(z)/r_s(z_d). After combining pre-reconstruction RSD analyses of the power spectrum monopole, quadrupole and bispectrum monopole; with post-reconstruction analysis of the BAO power spectrum monopole and quadrupole, we find f(zLOWZ)σ8(zLOWZ)=0.427±0.056f(z_{\rm LOWZ})\sigma_8(z_{\rm LOWZ})=0.427\pm 0.056, DA(zLOWZ)/rs(zd)=6.60±0.13D_A(z_{\rm LOWZ})/r_s(z_d)=6.60 \pm 0.13, H(zLOWZ)rs(zd)=(11.55±0.38)103kms1H(z_{\rm LOWZ})r_s(z_d)=(11.55\pm 0.38)10^3\,{\rm kms}^{-1} for the LOWZ sample, and f(zCMASS)σ8(zCMASS)=0.426±0.029f(z_{\rm CMASS})\sigma_8(z_{\rm CMASS})=0.426\pm 0.029, DA(zCMASS)/rs(zd)=9.39±0.10D_A(z_{\rm CMASS})/r_s(z_d)=9.39 \pm 0.10, H(zCMASS)rs(zd)=(14.02±0.22)103kms1H(z_{\rm CMASS})r_s(z_d)=(14.02\pm 0.22)10^3\,{\rm kms}^{-1} for the CMASS sample. We find general agreement with previous BOSS DR11 and DR12 measurements. Combining our dataset with {\it Planck15} we perform a null test of General Relativity (GR) through the γ\gamma-parametrisation finding γ=0.7330.069+0.068\gamma=0.733^{+0.068}_{-0.069}, which is 2.7σ\sim2.7\sigma away from the GR predictions.Comment: 34 pages, 22 figures, 8 tables. Accepted for publication in MNRAS. Data available at https://sdss3.org//science/boss_publications.ph

    SiC (SCS-6) Fiber Reinforced-Reaction Formed SiC Matrix Composites: Microstructure and Interfacial Properties

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    Microstructural and interfacial characterization of unidirectional SiC (SCS-6) fiber reinforced-reaction formed SiC (RFSC) composites has been carried out. Silicon-1.7 at.% molybdenum alloy was used as the melt infiltrant, instead of pure silicon, to reduce the activity of silicon in the melt as well as to reduce the amount of free silicon in the matrix. Electron microprobe analysis was used to evaluate the microstructure and phase distribution in these composites. The matrix is SiC with a bi-modal grain-size distribution and small amounts of MoSi2, silicon, and carbon. Fiber push-outs tests on these composites showed that a desirably low interfacial shear strength was achieved. The average debond shear stress at room temperature varied with specimen thickness from 29 to 64 MPa, with higher values observed for thinner specimens. Initial frictional sliding stresses showed little thickness dependence with values generally close to 30 MPa. Push-out test results showed very little change when the test temperature was increased to 800 C from room temperature, indicating an absence of significant residual stresses in the composite

    Eeg-Derived Estimators of Present and Future Cognitive Performance

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    Previous electroencephalography (EEG)-based fatigue-related research primarily focused on the association between concurrent cognitive performance and time-locked physiology. The goal of this study was to investigate the capability of EEG to assess the impact of fatigue on both present and future cognitive performance during a 20-min sustained attention task, the 3-choice active vigilance task (3CVT), that requires subjects to discriminate one primary target from two secondary non-target geometric shapes. The current study demonstrated the ability of EEG to estimate not only present, but also future cognitive performance, utilizing a single, combined reaction time (RT), and accuracy performance metric. The correlations between observed and estimated performance, for both present and future performance, were strong (up to 0.89 and 0.79, respectively). The models were able to consistently estimate “unacceptable” performance throughout the entire 3CVT, i.e., excessively missed responses and/or slow RTs, while acceptable performance was recognized less accurately later in the task. The developed models were trained on a relatively large dataset (n = 50 subjects) to increase stability. Cross-validation results suggested the models were not over-fitted. This study indicates that EEG can be used to predict gross-performance degradations 5–15 min in advance

    Nocturnal thoracoabdominal asynchrony in house dust mite-sensitive nonhuman primates

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    Nocturnal bronchoconstriction is a common symptom of asthma in humans, but is poorly documented in animal models. Thoracoabdominal asynchrony (TAA) is a noninvasive clinical indication of airway obstruction. In this study, respiratory inductive plethysmography (RIP) was used to document nocturnal TAA in house dust mite (HDM)-sensitive Cynomolgus macaques. Dynamic compliance (Cdyn) and lung resistance (RL) measured in anesthetized animals at rest and following exposure to HDM allergen, methacholine, and albuterol were highly correlated with three RIP parameters associated with TAA, ie, phase angle of the rib cage and abdomen waveforms (PhAng), baseline effort phase relation (eBPRL) and effort phase relation (ePhRL). Twenty-one allergic subjects were challenged with HDM early in the morning, and eBPRL and ePhRL were monitored for 20 hours after provocation. Fifteen of the allergic subjects exhibited gradual increases in eBPRL and ePhRL between midnight and 6 am, with peak activity at 4 am. However, as in humans, this nocturnal response was highly variable both between subjects and within subjects over time. The results document that TAA in this nonhuman primate model of asthma is highly correlated with Cdyn and RL, and demonstrate that animals exhibiting acute responses to allergen exposure during the day also exhibit nocturnal TAA
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