1,397 research outputs found

    Radiocarbon and Luminescence Dating at Flamingo Bay (38AK469): Implications for Site Formation Processes and Artifact Burial at a Carolina Bay

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    This Article is brought to you for free and open access by the Archaeology and Anthropology, South Carolina Institute of at Scholar Commons. It ha

    New Constraints on the Lyman Continuum Escape Fraction at z~1.3

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    We examine deep far-ultraviolet (1600 Angstrom) imaging of the Hubble Deep Field-North (HDFN) and the Hubble Ultra Deep Field (HUDF) to search for leaking Lyman continuum radiation from starburst galaxies at z~1.3. There are 21 (primarily sub-L*) galaxies with spectroscopic redshifts between 1.1<z<1.5 and none are detected in the far-UV. We fit stellar population templates to the galaxies' optical/near-infrared SEDs to determine the starburst age and level of dust attenuation, giving an accurate estimate of the intrinsic Lyman continuum ratio, f_1500/f_700, and allowing a conversion from f_700 limits to relative escape fractions. We show that previous high-redshift studies may have underestimated the amplitude of the Lyman Break, and thus the relative escape fraction, by a factor of ~2. Once the starburst age and intergalactic HI absorption are accounted for, 18 galaxies in our sample have limits to the relative escape fraction, f_esc,rel < 1.0 with some limits as low as f_esc,rel < 0.10 and a stacked limit of f_esc,rel < 0.08. This demonstrates, for the first time, that most sub-L* galaxies at high redshift do not have large escape fractions. When combined with a similar study of more luminous galaxies at the same redshift we show that, if all star-forming galaxies at z~1 have similar relative escape fractions, the value must be less than 0.14 (3 sigma). We also show that less than 20% (3 sigma) of star-forming galaxies at z~1 have relative escape fractions near unity. These limits contrast with the large escape fractions found at z~3 and suggest that the average escape fraction has decreased between z~3 and z~1. (Abridged)Comment: Accepted for publication in ApJ. aastex format. 39 pages, 11 figure

    Description of an ancient social bee trapped in amber using diagnostic radioentomology

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    The application of non-invasive imaging technologies using X-radiation (diagnostic radioentomology, ā€˜DRā€™) is demonstrated for the study of amber-entombed social bees. Here, we examine the external and internal morphology of an Early Miocene (Burdigalian) stingless bee (Apinae: Meliponini) from the Dominican Republic using non-destructive X-ray microtomography analysis. The study permits the accurate reconstruction of features otherwise obscured or impossible to visualize without destroying the sample and allows diagnosis of the specimen as a new species, Proplebeia adbita Greco and Engel

    The Evolution of the Galaxy Stellar Mass Function at z= 4-8: A Steepening Low-mass-end Slope with Increasing Redshift

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    We present galaxy stellar mass functions (GSMFs) at z=z= 4-8 from a rest-frame ultraviolet (UV) selected sample of āˆ¼\sim4500 galaxies, found via photometric redshifts over an area of āˆ¼\sim280 arcmin2^2 in the CANDELS/GOODS fields and the Hubble Ultra Deep Field. The deepest Spitzer/IRAC data yet-to-date and the relatively large volume allow us to place a better constraint at both the low- and high-mass ends of the GSMFs compared to previous space-based studies from pre-CANDELS observations. Supplemented by a stacking analysis, we find a linear correlation between the rest-frame UV absolute magnitude at 1500 \AA\ (MUVM_{\rm UV}) and logarithmic stellar mass (logā”Māˆ—\log M_*) that holds for galaxies with logā”(Māˆ—/MāŠ™)ā‰²10\log(M_*/M_{\odot}) \lesssim 10. We use simulations to validate our method of measuring the slope of the logā”Māˆ—\log M_*-MUVM_{\rm UV} relation, finding that the bias is minimized with a hybrid technique combining photometry of individual bright galaxies with stacked photometry for faint galaxies. The resultant measured slopes do not significantly evolve over z=z= 4-8, while the normalization of the trend exhibits a weak evolution toward lower masses at higher redshift. We combine the logā”Māˆ—\log M_*-MUVM_{\rm UV} distribution with observed rest-frame UV luminosity functions at each redshift to derive the GSMFs, finding that the low-mass-end slope becomes steeper with increasing redshift from Ī±=āˆ’1.55āˆ’0.07+0.08\alpha=-1.55^{+0.08}_{-0.07} at z=4z=4 to Ī±=āˆ’2.25āˆ’0.35+0.72\alpha=-2.25^{+0.72}_{-0.35} at z=8z=8. The inferred stellar mass density, when integrated over Māˆ—=108M_*=10^8-1013MāŠ™10^{13} M_{\odot}, increases by a factor of 10āˆ’2+3010^{+30}_{-2} between z=7z=7 and z=4z=4 and is in good agreement with the time integral of the cosmic star formation rate density.Comment: 27 pages, 17 figures, ApJ, in pres

    Improved Survival Associated with Neoadjuvant Chemoradiation in Patients with Clinical Stage IIIA(N2) Nonā€“Small-Cell Lung Cancer

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    IntroductionOptimal management of clinical stage IIIA-N2 nonā€“small-cell lung cancer (NSCLC) is controversial. This study examines whether neoadjuvant chemoradiation plus surgery improves survival rates when compared with other recommended treatment strategies.MethodsAdult patients from the National Cancer Database, with clinical stage IIIA-N2 disease definitively treated between 1998 and 2004 at American College of Surgeons Commission on Cancer accredited facilities, were included in the study. Treatment was defined as neoadjuvant chemoradiation plus either lobectomy (NeoCRT+L) or pneumonectomy (NeoCRT+P), lobectomy plus adjuvant therapy (L+AT), pneumonectomy plus adjuvant therapy (P+AT), and concurrent chemoradiation (CRT). Median follow-up and overall survival (OS) were defined from date of diagnosis to last contact. Five-year OS was estimated using Kaplanā€“Meier methods. Cox proportional hazard regression was used to estimate hazard ratios and 95% confidence intervals (CIs), adjusting for sociodemographic, clinical, and facility characteristics.ResultsMedian follow-up was 11.8 months for 11,242 eligible patients. Five-year OS was 33.5%, 20.7%, 20.3%, 13.35%, and 10.9% for NeoCRT+L, NeoCRT+P, L+AT, P+AT, and CRT, respectively (p < 0.0001). On multivariable analysis, the estimated hazard ratio was 0.51 (CI: 0.45ā€“0.58) for NeoCRT+L; 0.77 (0.63ā€“0.95) for NeoCRT+P; 0.66 (0.59ā€“0.75) for L+AT; 0.69 (0.54ā€“0.88) for P+AT; and 1.0 (reference) for the CRT group. Comorbidity did not attenuate the relationship between treatment and survival.ConclusionThis large study demonstrates that patients with clinical stage IIIA-N2 NSCLC, who underwent neoadjuvant chemoradiation followed by lobectomy, were associated with an improved survival

    Publishing and sharing multi-dimensional image data with OMERO

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    Imaging data are used in the life and biomedical sciences to measure the molecular and structural composition and dynamics of cells, tissues, and organisms. Datasets range in size from megabytes to terabytes and usually contain a combination of binary pixel data and metadata that describe the acquisition process and any derived results. The OMERO image data management platform allows users to securely share image datasets according to specific permissions levels: data can be held privately, shared with a set of colleagues, or made available via a public URL. Users control access by assigning data to specific Groups with defined membership and access rights. OMEROā€™s Permission system supports simple data sharing in a lab, collaborative data analysis, and even teaching environments. OMERO software is open source and released by the OME Consortium at www.openmicroscopy.org

    The Unusual Infrared Object HDF-N J123656.3+621322

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    We describe an object in the Hubble Deep Field North with very unusual near-infrared properties. It is readily visible in Hubble Space Telescope NICMOS images at 1.6um and from the ground at 2.2um, but is undetected (with signal-to-noise <~ 2) in very deep WFPC2 and NICMOS data from 0.3 to 1.1um. The f_nu flux density drops by a factor >~ 8.3 (97.7% confidence) from 1.6 to 1.1um. The object is compact but may be slightly resolved in the NICMOS 1.6um image. In a low-resolution, near-infrared spectrogram, we find a possible emission line at 1.643um, but a reobservation at higher spectral resolution failed to confirm the line, leaving its reality in doubt. We consider various hypotheses for the nature of this object. Its colors are unlike those of known galactic stars, except perhaps the most extreme carbon stars or Mira variables with thick circumstellar dust shells. It does not appear to be possible to explain its spectral energy distribution as that of a normal galaxy at any redshift without additional opacity from either dust or intergalactic neutral hydrogen. The colors can be matched by those of a dusty galaxy at z >~ 2, by a maximally old elliptical galaxy at z >~ 3 (perhaps with some additional reddening), or by an object at z >~ 10 whose optical and 1.1um light have been suppressed by the intergalactic medium. Under the latter hypothesis, if the luminosity results from stars and not an AGN, the object would resemble a classical, unobscured protogalaxy, with a star formation rate >~ 100 M_sun/yr. Such UV-bright objects are evidently rare at 2 < z < 12.5, however, with a space density several hundred times lower than that of present-day L* galaxies.Comment: Accepted for publication in the Astrophysical Journal. 27 pages, LaTeX, with 7 figures (8 files); citations & references updated + minor format change

    Life on Jackson Creek, Smith County, Texas: Archeological Investigations of a 14th Century Caddo Domicile at the Leaning Rock Site (41SM325)

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    The 14th century Caddo Leaning Rock site was initially discovered in the Fall of 2004. It was located during reconnaissance to search out a location for the survey portion of the Texas Archeologica! Society\u27s Academy IO I held in Tyler in February 2005. This was not a formal survey with transect lines. nor one using regularly spaced shovel tests. but was rather more of a windshield \u27 type survey, consisting of driving across pasture lands looking at gopher mounds and checking fore, evidence of archeological deposits on likely looking landforms. !n this area. landform and soil type seem to be the major determining factors in locating Caddo sites. The sandy soils in the scattered gopher mounds appeared almost white. especially in droughty conditions that prevailed at the time. causing an area with darker mounds of soil to catch my attention. Pocket gophers (G. breviceps) can play havoc with buried archeological deposits but can also be useful in bringing buried soils along with archeological materials to the surface from their underground tunnel system. While this dark area could have been the result of past historic land clearing and burning activities. a closer inspection revealed burned bone. mussel she!L and Caddo sherds mixed in the dark brown soils in the scattered gopher mounds. The next step was to record the site with the State of Texas, obtaining the trinomial 41SM325. It is common practice to also gin: sites informal names and after recording several hundred sites, selecting a name becomes a challenge. One large sandstone slab, pan of the R-horizon that is exposed around the margins of Leaning Rock. was unearthed during prior landclearing activities and pushed up against a lonely pine tree on the northern margins of the site: consequently the nom de plume Leaning Rock

    Political Regimes and Sovereign Credit Risk in Europe, 1750-1913

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    This article uses a new panel data set to perform a statistical analysis of political regimes and sovereign credit risk in Europe from 1750 to 1913. Old Regime polities typically suffered from fiscal fragmentation and absolutist rule. By the start of World War I, however, many such countries had centralized institutions and limited government. Panel regressions indicate that centralized and?or limited regimes were associated with significant improvements in credit risk relative to fragmented and absolutist ones. Structural break tests also reveal close relationships between major turning points in yield series and political transformations
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