725 research outputs found

    Computationally designed libraries of fluorescent proteins evaluated by preservation and diversity of function

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    To determine which of seven library design algorithms best introduces new protein function without destroying it altogether, seven combinatorial libraries of green fluorescent protein variants were designed and synthesized. Each was evaluated by distributions of emission intensity and color compiled from measurements made in vivo. Additional comparisons were made with a library constructed by error-prone PCR. Among the designed libraries, fluorescent function was preserved for the greatest fraction of samples in a library designed by using a structure-based computational method developed and described here. A trend was observed toward greater diversity of color in designed libraries that better preserved fluorescence. Contrary to trends observed among libraries constructed by error-prone PCR, preservation of function was observed to increase with a library's average mutation level among the four libraries designed with structure-based computational methods

    Turbulent Gas Flows in the Rosette and G216-2.5 Molecular Clouds: Assessing Turbulent Fragmentation Descriptions of Star Formation

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    The role of turbulent fragmentation in regulating the efficiency of star formation in interstellar clouds is examined from new wide field imaging of 12CO and 13CO J=1-0 emission from the Rosette and G216-2.5 molecular clouds. The Rosette molecular cloud is a typical star forming giant molecular cloud and G215-2.5 is a massive molecular cloud with no OB stars and very little low mass star formation. The properties of the turbulent gas flow are derived from the set of eigenvectors and eigenimages generated by Principal Component Analysis of the spectroscopic data cubes. While the two clouds represent quite divergent states of star formation activity, the velocity structure functions for both clouds are similar. The sonic scale, lambda_S, defined as the spatial scale at which turbulent velocity fluctuations are equivalent to the local sound speed, and the turbulent Mach number evaluated at 1 pc, M_{1pc}, are derived for an ensemble of clouds including the Rosette and, G216-2.5 regions that span a large range in star formation activity. We find no evidence for the positive correlations between these quantities and the star formation efficiency, that are predicted by turbulent fragmentation models. A correlation does exist between the star formation efficiency and the sonic scale for a subset of clouds with L_{FIR}/M(H_2) > 1 that are generating young stellar clusters. Turbulent fragmentation must play a limited and non-exclusive role in determining the yield of stellar masses within interstellar clouds.Comment: Accepted by ApJ, 22 pages, 7 figure

    Self-reported health, perceived racial discrimination, and skin color in african americans in the CARDIA study

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    http://deepblue.lib.umich.edu/bitstream/2027.42/61518/1/Borrell_Self-reported-health,-perceived-racial-discrimination,-and-skin-color-in-African-Americans-in-the-CARDIA-study_2006.pd

    Keck Spectroscopy of 3<z<7 Faint Lyman Break Galaxies: The Importance of Nebular Emission in Understanding the Specific Star Formation Rate and Stellar Mass Density

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    The physical properties inferred from the SEDs of z>3 galaxies have been influential in shaping our understanding of early galaxy formation and the role galaxies may play in cosmic reionization. Of particular importance is the stellar mass density at early times which represents the integral of earlier star formation. An important puzzle arising from the measurements so far reported is that the specific star formation rates (sSFR) evolve far less rapidly than expected in most theoretical models. Yet the observations underpinning these results remain very uncertain, owing in part to the possible contamination of rest-optical broadband light from strong nebular emission lines. To quantify the contribution of nebular emission to broad-band fluxes, we investigate the SEDs of 92 spectroscopically-confirmed galaxies in the redshift range 3.8<z<5.0 chosen because the H-alpha line lies within the Spitzer/IRAC 3.6 um filter. We demonstrate that the 3.6 um flux is systematically in excess of that expected from stellar continuum, which we derive by fitting the SED with population synthesis models. No such excess is seen in a control sample at 3.1<z<3.6 in which there is no nebular contamination in the IRAC filters. From the distribution of our 3.6 um flux excesses, we derive an H-alpha equivalent width (EW) distribution. The mean rest-frame H-alpha EW we infer at 3.8<z<5.0 (270 A) indicates that nebular emission contributes at least 30% of the 3.6 um flux. Via our empirically-derived EW distribution we correct the available stellar mass densities and show that the sSFR evolves more rapidly at z>4 than previously thought, supporting up to a 5x increase between z~2 and 7. Such a trend is much closer to theoretical expectations. Given our findings, we discuss the prospects for verifying quantitatively the nebular emission line strengths prior to the launch of the James Webb Space Telescope.Comment: 16 pages, 9 figures, submitted to Ap

    Heterogenized Pyridine-Substituted Cobalt(II) Phthalocyanine Yields Reduction of CO2 by Tuning the Electron Affinity of the Co Center

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    Conversion of CO2 to reduced products is a promising route to alleviate irreversible climate change. Here we report the synthesis of a Co-based phthalocyanine with pyridine moieties (CoPc-Pyr), which is supported on a carbon electrode and shows Faradaic efficiency ∌90% for CO at 490 mV of overpotential (-0.6 V vs reversible hydrogen electrode (RHE)). In addition, its catalytic activity at -0.7 V versus RHE surpasses other Co-based molecular and metal-organic framework catalysts for CO2 reduction at this bias. Density functional theory calculations show that pyridine moieties enhance CO2 adsorption and electron affinity of the Co center by an inductive effect, thus lowering the overpotential necessary for CO2 conversion. Our study shows that CoPc-Pyr reduces CO2 at lower overpotential and with higher activity than noble metal electrodes, such as silver

    Training of Instrumentalists and Development of New Technologies on SOFIA

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    This white paper is submitted to the Astronomy and Astrophysics 2010 Decadal Survey (Astro2010)1 Committee on the State of the Profession to emphasize the potential of the Stratospheric Observatory for Infrared Astronomy (SOFIA) to contribute to the training of instrumentalists and observers, and to related technology developments. This potential goes beyond the primary mission of SOFIA, which is to carry out unique, high priority astronomical research. SOFIA is a Boeing 747SP aircraft with a 2.5 meter telescope. It will enable astronomical observations anywhere, any time, and at most wavelengths between 0.3 microns and 1.6 mm not accessible from ground-based observatories. These attributes, accruing from the mobility and flight altitude of SOFIA, guarantee a wealth of scientific return. Its instrument teams (nine in the first generation) and guest investigators will do suborbital astronomy in a shirt-sleeve environment. The project will invest $10M per year in science instrument development over a lifetime of 20 years. This, frequent flight opportunities, and operation that enables rapid changes of science instruments and hands-on in-flight access to the instruments, assure a unique and extensive potential - both for training young instrumentalists and for encouraging and deploying nascent technologies. Novel instruments covering optical, infrared, and submillimeter bands can be developed for and tested on SOFIA by their developers (including apprentices) for their own observations and for those of guest observers, to validate technologies and maximize observational effectiveness.Comment: 10 pages, no figures, White Paper for Astro 2010 Survey Committee on State of the Professio

    A forgotten figure in Siouan and Caddoan linguistics: Samuel Stehman Haldeman.

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    The Siouan family comprises some twenty languages, historically spoken across a broad swath of the central North American plains and woodlands, as well as in parts of the southeastern United States. In spite of its geographical extent and diversity, and the size and importance of several Siouan-speaking tribes, this family has received relatively little attention in the linguistic literature and many of the individual Siouan languages are severely understudied. This volume aims to make work on Siouan languages more broadly available and to encourage deeper investigation of the myriad typological, theoretical, descriptive, and pedagogical issues they raise. The 17 chapters in this volume present a broad range of current Siouan research, focusing on various Siouan languages, from a variety of linguistic perspectives: historical-genetic, philological, applied, descriptive, formal/generative, and comparative/typological. The editors' preface summarizes characteristic features of the Siouan family, including head-final and "verb-centered" syntax, a complex system of verbal affixes including applicatives and subject-possessives, head-internal relative clauses, gendered speech markers, stop-systems including ejectives, and a preference for certain prosodic and phonotactic patterns. The volume is dedicated to the memory of Professor Robert L. Rankin, a towering figure in Siouan linguistics throughout his long career, who passed away in February of 2014

    Advances in the study of Siouan languages and linguistics

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    The Siouan family comprises some twenty languages, historically spoken across a broad swath of the central North American plains and woodlands, as well as in parts of the southeastern United States. In spite of its geographical extent and diversity, and the size and importance of several Siouan-speaking tribes, this family has received relatively little attention in the linguistic literature and many of the individual Siouan languages are severely understudied. This volume aims to make work on Siouan languages more broadly available and to encourage deeper investigation of the myriad typological, theoretical, descriptive, and pedagogical issues they raise. The 17 chapters in this volume present a broad range of current Siouan research, focusing on various Siouan languages, from a variety of linguistic perspectives: historical-genetic, philological, applied, descriptive, formal/generative, and comparative/typological. The editors' preface summarizes characteristic features of the Siouan family, including head-final and "verb-centered" syntax, a complex system of verbal affixes including applicatives and subject-possessives, head-internal relative clauses, gendered speech markers, stop-systems including ejectives, and a preference for certain prosodic and phonotactic patterns. The volume is dedicated to the memory of Professor Robert L. Rankin, a towering figure in Siouan linguistics throughout his long career, who passed away in February of 2014

    Advances in the study of Siouan languages and linguistics

    Get PDF
    The Siouan family comprises some twenty languages, historically spoken across a broad swath of the central North American plains and woodlands, as well as in parts of the southeastern United States. In spite of its geographical extent and diversity, and the size and importance of several Siouan-speaking tribes, this family has received relatively little attention in the linguistic literature and many of the individual Siouan languages are severely understudied. This volume aims to make work on Siouan languages more broadly available and to encourage deeper investigation of the myriad typological, theoretical, descriptive, and pedagogical issues they raise. The 17 chapters in this volume present a broad range of current Siouan research, focusing on various Siouan languages, from a variety of linguistic perspectives: historical-genetic, philological, applied, descriptive, formal/generative, and comparative/typological. The editors' preface summarizes characteristic features of the Siouan family, including head-final and "verb-centered" syntax, a complex system of verbal affixes including applicatives and subject-possessives, head-internal relative clauses, gendered speech markers, stop-systems including ejectives, and a preference for certain prosodic and phonotactic patterns. The volume is dedicated to the memory of Professor Robert L. Rankin, a towering figure in Siouan linguistics throughout his long career, who passed away in February of 2014

    Advances in the study of Siouan languages and linguistics

    Get PDF
    The Siouan family comprises some twenty languages, historically spoken across a broad swath of the central North American plains and woodlands, as well as in parts of the southeastern United States. In spite of its geographical extent and diversity, and the size and importance of several Siouan-speaking tribes, this family has received relatively little attention in the linguistic literature and many of the individual Siouan languages are severely understudied. This volume aims to make work on Siouan languages more broadly available and to encourage deeper investigation of the myriad typological, theoretical, descriptive, and pedagogical issues they raise. The 17 chapters in this volume present a broad range of current Siouan research, focusing on various Siouan languages, from a variety of linguistic perspectives: historical-genetic, philological, applied, descriptive, formal/generative, and comparative/typological. The editors' preface summarizes characteristic features of the Siouan family, including head-final and "verb-centered" syntax, a complex system of verbal affixes including applicatives and subject-possessives, head-internal relative clauses, gendered speech markers, stop-systems including ejectives, and a preference for certain prosodic and phonotactic patterns. The volume is dedicated to the memory of Professor Robert L. Rankin, a towering figure in Siouan linguistics throughout his long career, who passed away in February of 2014
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