3,296 research outputs found

    Frontier Fields: High-Redshift Predictions and Early Results

    Full text link
    The Frontier Fields program is obtaining deep Hubble and Spitzer Space Telescope images of new "blank" fields and nearby fields gravitationally lensed by massive galaxy clusters. The Hubble images of the lensed fields are revealing nJy sources (AB mag > 31), the faintest galaxies yet observed. In this paper, we present high-redshift (z > 6) number count predictions for the full program and candidates in three of the first Hubble Frontier Fields images. The full program will transform our understanding of galaxy evolution in the first 600 million years (z > 9). Where previous programs yielded perhaps a dozen z > 9 candidates, the Frontier Fields may yield ~70 (~6 per field). We base this estimate on an extrapolation of luminosity functions observed between 4 < z < 8 and gravitational lensing models submitted by the community. However, in the first two deep infrared Hubble images obtained to date, we find z ~ 8 candidates but no strong candidates at z > 9. This might suggest a deficit of faint z > 9 galaxies as also reported in the Ultra Deep Field (even while excesses of brighter z > 9 galaxies were reported in shallower fields). At these redshifts, cosmic variance (field-to-field variation) is expected to be significant (greater than +/-50%) and include clustering of early galaxies formed in overdensities. The full Frontier Fields program will significantly mitigate this uncertainty by observing six independent sightlines each with a lensing cluster and nearby blank field.Comment: Submitted for publication in the Astrophysical Journal. 15 pages, 17 figure

    The CombiUgi Project and Closing the Open Science Loop

    Get PDF
    This presentation combines 2 blog posts explaining the CombiUgi project and the predicted anti-tumor activity of a virtual library of 68,000 compounds

    Wage incentives - application at Dennison Manufacturing Company.

    Full text link
    Thesis (M.B.A.)--Boston Universit

    The Private Bar And The Public Lawyer: An Essential Partnership

    Get PDF
    Historically, the leadership and momentum for making legal services available to the poor came from the organized bar

    Professional Services Offered in Rural, Mixed-Animal Veterinary Practices

    Get PDF
    Rural, mixed animal veterinary practices offer a variety of professional services to their clientele. Practitioners must decide which services to offer and how much time to dedicate to each offering. These decisions are influenced by the perceived need for each service in the area and the potential income that can be generated from the specific service

    Successor CEO Functional And Educational Backgrounds: Influence Of Predecessor Characteristics And Performance Antecedents

    Get PDF
    This study seeks to examine if boards consider CEO educational and functional background when choosing a new CEO. It also examines which factors determine whether the board of directors will seek an incoming CEO with a different educational and/or functional background from that of the current CEO. Using a sample of 832 successions between 1992 and 2009, we found that the outgoing CEO characteristics and the firm characteristics influence the selection of the incoming CEO functional backgrounds. We found an increase in the likelihood of firms hiring incoming CEOs with the same functional backgrounds as the outgoing CEOs. Incoming CEOs with functional backgrounds in engineering/manufacturing are more likely to be hired by research-oriented firms.Incoming CEOs with functional backgrounds in accounting/finance are more likely to be hired by poorly performing firms. We also find that firms are more likely to change the functional background of the successor relative to the predecessor when there has been poor prior performance and the firm has higher institutional investor ownership

    Rethinking Educational Design in New\u27 School Construction

    Get PDF
    The primary impetus to new school construction, of course, typically involves relieving overcrowding or replacing outdated or dangerous facilities. Bradley (1996), however, in a study about the role of architecture in education, notes that the physical structure of a school has the potential to be a vehicle for change. In other words, the design. of school facilities can inspire alterations in the nature, quality, and future direction of what goes on inside. The present study sought to determine the extent to which five school systems in Virginia took advantage of building a new secondary school to address the need for fundamental educational change

    Making more of little data:Improving low-resource automatic speech recognition using data augmentation

    Get PDF
    The performance of automatic speech recognition (ASR) systems has advanced substantially in recent years, particularly for languages for which a large amount of transcribed speech is available. Unfortunately, for low-resource languages, such as minority languages, regional languages or dialects, ASR performance generally remains much lower. In this study, we investigate whether data augmentation techniques could help improve low-resource ASR performance, focusing on four typologically diverse minority languages or language variants (West Germanic: Gronings, West-Frisian; Malayo-Polynesian: Besemah, Nasal). For all four languages, we examine the use of self-training, where an ASR system trained with the available human-transcribed data is used to generate transcriptions, which are then combined with the original data to train a new ASR system. For Gronings, for which there was a pre-existing text-to-speech (TTS) system available, we also examined the use of TTS to generate ASR training data from text-only sources. We find that using a self-training approach consistently yields improved performance (a relative WER reduction up to 20.5% compared to using an ASR system trained on 24 minutes of manually transcribed speech). The performance gain from TTS augmentation for Gronings was even stronger (up to 25.5% relative reduction in WER compared to a system based on 24 minutes of manually transcribed speech). In sum, our results show the benefit of using self-training or (if possible) TTS-generated data as an efficient solution to overcome the limitations of data availability for resource-scarce languages in order to improve ASR performance

    The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei

    Get PDF
    We reinvestigate the relationship between the characteristic broad-line region size (R_blr) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of R_blr for a large number of active galactic nuclei (AGNs) from Peterson et al. Using their determinations of R_blr for a large sample of AGNs and two different regression methods, we investigate the robustness of our correlation results as a function of data sub-sample and regression technique. Though small systematic differences were found depending on the method of analysis, our results are generally consistent. Assuming a power-law relation R_blr \propto L^\alpha, we find the mean best-fitting \alpha is about 0.67+/-0.05 for the optical continuum and the broad H\beta luminosity, about 0.56+/-0.05 for the UV continuum luminosity, and about 0.70+/-0.14 for the X-ray luminosity. We also find an intrinsic scatter of about 40% in these relations. The disagreement of our results with the theoretical expected slope of 0.5 indicates that the simple assumption of all AGNs having on average same ionization parameter, BLR density, column density, and ionizing spectral energy distribution, is not valid and there is likely some evolution of a few of these characteristics along the luminosity scale.Comment: 11 pages, 2 figures, emulateapj, accepted for publication in The Astrophysical Journa
    • …
    corecore