WorldWideScience

Sample records for quasar target selection

  1. THINK OUTSIDE THE COLOR BOX: PROBABILISTIC TARGET SELECTION AND THE SDSS-XDQSO QUASAR TARGETING CATALOG

    International Nuclear Information System (INIS)

    Bovy, Jo; Hogg, David W.; Weaver, Benjamin A.; Hennawi, Joseph F.; Myers, Adam D.; Kirkpatrick, Jessica A.; Schlegel, David J.; Ross, Nicholas P.; Sheldon, Erin S.; McGreer, Ian D.; Schneider, Donald P.

    2011-01-01

    We present the SDSS-XDQSO quasar targeting catalog for efficient flux-based quasar target selection down to the faint limit of the Sloan Digital Sky Survey (SDSS) catalog, even at medium redshifts (2.5 ∼ 3.5) quasar probabilities for all 160,904,060 point sources with dereddened i-band magnitude between 17.75 and 22.45 mag in the 14,555 deg 2 of imaging from SDSS Data Release 8. The catalog can be used to define a uniformly selected and efficient low- or medium-redshift quasar survey, such as that needed for the SDSS-III's Baryon Oscillation Spectroscopic Survey project. We show that the XDQSO technique performs as well as the current best photometric quasar-selection technique at low redshift, and outperforms all other flux-based methods for selecting the medium-redshift quasars of our primary interest. We make code to reproduce the XDQSO quasar target selection publicly available.

  2. Think Outside The Color Box: Probabilistic Target Selection And The SDSS-XDQSO Quasar Targeting Catalog

    International Nuclear Information System (INIS)

    Bovy, J.; Sheldon, E.; Hennawi, J.F.; Hogg, D.W.; Myers, A.D.

    2011-01-01

    We present the SDSS-XDQSO quasar targeting catalog for efficient flux-based quasar target selection down to the faint limit of the Sloan Digital Sky Survey (SDSS) catalog, even at medium redshifts (2.5 ∼ 3.5) quasar probabilities for all 160,904,060 point sources with dereddened i-band magnitude between 17.75 and 22.45 mag in the 14,555 deg 2 of imaging from SDSS Data Release 8. The catalog can be used to define a uniformly selected and efficient low- or medium-redshift quasar survey, such as that needed for the SDSS-III's Baryon Oscillation Spectroscopic Survey project. We show that the XDQSO technique performs as well as the current best photometric quasar-selection technique at low redshift, and outperforms all other flux-based methods for selecting the medium-redshift quasars of our primary interest. We make code to reproduce the XDQSO quasar target selection publicly available.

  3. THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: QUASAR TARGET SELECTION FOR DATA RELEASE NINE

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Nicholas P.; Kirkpatrick, Jessica A.; Carithers, William C.; Ho, Shirley [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Myers, Adam D. [Department of Astronomy, MC-221, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Sheldon, Erin S. [Brookhaven National Laboratory, Blgd 510, Upton, NY 11375 (United States); Yeche, Christophe; Aubourg, Eric [CEA, Centre de Saclay, IRFU, 91191 Gif-sur-Yvette (France); Strauss, Michael A.; Lee, Khee-Gan [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Bovy, Jo; Blanton, Michael R.; Hogg, David W. [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Croft, Rupert A. C. [Bruce and Astrid McWilliams Center for Cosmology, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Da Silva, Robert [Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA 95064 (United States); Dawson, Kyle [Department of Physics and Astronomy, University of Utah, UT (United States); Eisenstein, Daniel J. [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Hennawi, Joseph F., E-mail: npross@lbl.gov [Max-Planck-Institut fuer Astronomie, Konigstuhl 17, 69117 Heidelberg (Germany); and others

    2012-03-01

    The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year spectroscopic survey of 10,000 deg{sup 2}, achieved first light in late 2009. One of the key goals of BOSS is to measure the signature of baryon acoustic oscillations (BAOs) in the distribution of Ly{alpha} absorption from the spectra of a sample of {approx}150,000 z > 2.2 quasars. Along with measuring the angular diameter distance at z Almost-Equal-To 2.5, BOSS will provide the first direct measurement of the expansion rate of the universe at z > 2. One of the biggest challenges in achieving this goal is an efficient target selection algorithm for quasars in the redshift range 2.2 < z < 3.5, where their colors tend to overlap those of the far more numerous stars. During the first year of the BOSS survey, quasar target selection (QTS) methods were developed and tested to meet the requirement of delivering at least 15 quasars deg{sup -2} in this redshift range, with a goal of 20 out of 40 targets deg{sup -2} allocated to the quasar survey. To achieve these surface densities, the magnitude limit of the quasar targets was set at g {<=} 22.0 or r {<=} 21.85. While detection of the BAO signature in the distribution of Ly{alpha} absorption in quasar spectra does not require a uniform target selection algorithm, many other astrophysical studies do. We have therefore defined a uniformly selected subsample of 20 targets deg{sup -2}, for which the selection efficiency is just over 50% ({approx}10 z > 2.20 quasars deg{sup -2}). This 'CORE' subsample will be fixed for Years Two through Five of the survey. For the remaining 20 targets deg{sup -2}, we will continue to develop improved selection techniques, including the use of additional data sets beyond the Sloan Digital Sky Survey (SDSS) imaging data. In this paper, we describe the evolution and implementation of the BOSS QTS algorithms during the first two years of BOSS operations (through 2011 July), in support of the science investigations

  4. RADIO-SELECTED QUASARS IN THE SLOAN DIGITAL SKY SURVEY

    International Nuclear Information System (INIS)

    McGreer, Ian D.; Helfand, David J.; White, Richard L.

    2009-01-01

    We have conducted a pilot survey for z > 3.5 quasars by combining the FIRST radio survey with the Sloan Digital Sky Survey (SDSS). While SDSS already targets FIRST sources for spectroscopy as quasar candidates, our survey includes fainter quasars and greatly improves the discovery rate by using strict astrometric criteria for matching the radio and optical positions. Our method allows for selection of high-redshift quasars with less color bias than with optical selection, as using radio selection essentially eliminates stellar contamination. We report the results of spectroscopy for 45 candidates, including 29 quasars in the range 0.37 3.5. We compare quasars selected using radio and optical criteria, and find that radio-selected quasars have a much higher fraction of moderately reddened objects. We derive a radio-loud quasar luminosity function at 3.5 < z < 4.0, and find that it is in good agreement with expectations from prior SDSS results.

  5. Various Approaches for Targeting Quasar Candidates

    Science.gov (United States)

    Zhang, Y.; Zhao, Y.

    2015-09-01

    With the establishment and development of space-based and ground-based observational facilities, the improvement of scientific output of high-cost facilities is still a hot issue for astronomers. The discovery of new and rare quasars attracts much attention. Different methods to select quasar candidates are in bloom. Among them, some are based on color cuts, some are from multiwavelength data, some rely on variability of quasars, some are based on data mining, and some depend on ensemble methods.

  6. Space Density of Optically Selected Type 2 Quasars

    Science.gov (United States)

    Reyes, Reinabelle; Zakamska, Nadia L.; Strauss, Michael A.; Green, Joshua; Krolik, Julian H.; Shen, Yue; Richards, Gordon T.; Anderson, Scott F.; Schneider, Donald P.

    2008-12-01

    Type 2 quasars are luminous active galactic nuclei whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey, selected based on their optical emission lines. The catalog contains 887 objects with redshifts z < 0.83; this is 6 times larger than the previous version and is by far the largest sample of type 2 quasars in the literature. We derive the [O III]5007 luminosity function (LF) for 108.3 L sun < L [O III] < 1010 L sun (corresponding to intrinsic luminosities up to M[2500 Å] ~= -28 mag or bolometric luminosities up to 4 × 1047 erg s-1). This LF provides robust lower limits to the actual space density of obscured quasars due to our selection criteria, the details of the spectroscopic target selection, and other effects. We derive the equivalent LF for the complete sample of type 1 (unobscured) quasars and determine the ratio of type 2 to type 1 quasar number densities. Our data constrain this ratio to be at least ~1.5:1 for 108.3 L sun < L [O III] < 109.5 L sun at z < 0.3, and at least ~1.2:1 for L [O III] ~ 1010 L sun at 0.3 < z < 0.83. Type 2 quasars are at least as abundant as type 1 quasars in the relatively nearby universe (z <~ 0.8) for the highest luminosities.

  7. SELECTING QUASARS BY THEIR INTRINSIC VARIABILITY

    International Nuclear Information System (INIS)

    Schmidt, Kasper B.; Rix, Hans-Walter; Jester, Sebastian; Hennawi, Joseph F.; Marshall, Philip J.; Dobler, Gregory

    2010-01-01

    We present a new and simple technique for selecting extensive, complete, and pure quasar samples, based on their intrinsic variability. We parameterize the single-band variability by a power-law model for the light-curve structure function, with amplitude A and power-law index γ. We show that quasars can be efficiently separated from other non-variable and variable sources by the location of the individual sources in the A-γ plane. We use ∼60 epochs of imaging data, taken over ∼5 years, from the SDSS stripe 82 (S82) survey, where extensive spectroscopy provides a reference sample of quasars, to demonstrate the power of variability as a quasar classifier in multi-epoch surveys. For UV-excess selected objects, variability performs just as well as the standard SDSS color selection, identifying quasars with a completeness of 90% and a purity of 95%. In the redshift range 2.5 < z < 3, where color selection is known to be problematic, variability can select quasars with a completeness of 90% and a purity of 96%. This is a factor of 5-10 times more pure than existing color selection of quasars in this redshift range. Selecting objects from a broad griz color box without u-band information, variability selection in S82 can afford completeness and purity of 92%, despite a factor of 30 more contaminants than quasars in the color-selected feeder sample. This confirms that the fraction of quasars hidden in the 'stellar locus' of color space is small. To test variability selection in the context of Pan-STARRS 1 (PS1) we created mock PS1 data by down-sampling the S82 data to just six epochs over 3 years. Even with this much sparser time sampling, variability is an encouragingly efficient classifier. For instance, a 92% pure and 44% complete quasar candidate sample is attainable from the above griz-selected catalog. Finally, we show that the presented A-γ technique, besides selecting clean and pure samples of quasars (which are stochastically varying objects), is also

  8. THE EXTENDED HIGH A ( V ) QUASAR SURVEY: SEARCHING FOR DUSTY ABSORBERS TOWARD MID-INFRARED-SELECTED QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Krogager, J.-K.; Noterdaeme, P. [Institut d’Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, F-75014 Paris (France); Fynbo, J. P. U.; Heintz, K. E.; Vestergaard, M. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark); Geier, S. [Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain); Ledoux, C. [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19 (Chile); Møller, P. [European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching bei München (Germany); Venemans, B. P. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

    2016-11-20

    We present the results of a new spectroscopic survey for dusty intervening absorption systems, particularly damped Ly α absorbers (DLAs), toward reddened quasars. The candidate quasars are selected from mid-infrared photometry from the Wide-field Infrared Survey Explorer combined with optical and near-infrared photometry. Out of 1073 candidates, we secure low-resolution spectra for 108 using the Nordic Optical Telescope on La Palma, Spain. Based on the spectra, we are able to classify 100 of the 108 targets as quasars. A large fraction (50%) is observed to have broad absorption lines (BALs). Moreover, we find six quasars with strange breaks in their spectra, which are not consistent with regular dust reddening. Using template fitting, we infer the amount of reddening along each line of sight ranging from A ( V ) ≈ 0.1 to 1.2 mag (assuming a Small Magellanic Cloud extinction curve). In four cases, the reddening is consistent with dust exhibiting the 2175 Å feature caused by an intervening absorber, and for two of these, an Mg ii absorption system is observed at the best-fit absorption redshift. In the rest of the cases, the reddening is most likely intrinsic to the quasar. We observe no evidence for dusty DLAs in this survey. However, the large fraction of BAL quasars hampers the detection of absorption systems. Out of the 50 non-BAL quasars, only 28 have sufficiently high redshift to detect Ly α in absorption.

  9. Far-infrared properties of optically selected quasars

    International Nuclear Information System (INIS)

    Edelson, R.A.

    1986-01-01

    The far-infrared properties of 10, optically selected quasars were studied on the basis of pointed IRAS observations and ground-based near-infrared and radio measurements. Nine of these quasars were detected in at least three IRAS bands. The flat spectral energy distributions characterizing these optically selected quasars together with large 60-100-micron luminosities suggest that the infrared emission is dominated by nonthermal radiation. Seven of the nine quasars with far-infrared detections were found to have low-frequency turnovers. 12 references

  10. Space density of optically-selected type 2 quasars

    OpenAIRE

    Reyes, Reinabelle; Zakamska, Nadia L.; Strauss, Michael A.; Green, Joshua; Krolik, Julian H.; Shen, Yue; Richards, Gordon; Anderson, Scott; Schneider, Donald

    2008-01-01

    Type 2 quasars are luminous active galactic nuclei (AGN) whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey (SDSS), selected based on their optical emission lines. The catalog contains 887 objects with redshifts z < 0.83; this is six times larger than the previous version and is by far the largest sample of type 2 quasars in the literature. We derive the [OIII]5008 luminosity function for...

  11. Quasars.

    Science.gov (United States)

    Smith, H J

    1966-11-01

    A short historical outline of the discovery and a description of observed properties of quasars introduces questions as to their nature. Some of the principal arguments concerning their reality, distance, intrinsic properties and age lead to the conclusion that, while there is room for other points of view; a strong case can be made for the interpretation, on which quasars are the most distant observable objects in the known universe. To produce such luminosities over times of thousands to millions of years requires the presence of millions of solar masses. For each quasar this enormous mass may be concentrated into a single object, in which case novel physics comes into play. Whatever the final interpretation, quasars seem certain to illuminate such questions as the origin and evolution of galaxies, perhaps also the structure and origin of the universe.

  12. GALEX FAR-ULTRAVIOLET COLOR SELECTION OF UV-BRIGHT HIGH-REDSHIFT QUASARS

    International Nuclear Information System (INIS)

    Worseck, Gabor; Prochaska, J. Xavier

    2011-01-01

    We study the small population of high-redshift (z em >2.7) quasars detected by the Galaxy Evolution Explorer(GALEX), whose far-UV emission is not extinguished by intervening H I Lyman limit systems. These quasars are of particular importance to detect intergalactic He II absorption along their sight lines. We correlate almost all verified z em >2.7 quasars to the GALEX GR4 source catalog covering ∼ 25,000 deg 2 , yielding 304 sources detected at signal-to-noise ratio (S/N) >3. However, ∼50% of these are only detected in the GALEX NUV band, signaling the truncation of the FUV flux by low-redshift optically thick Lyman limit systems. We exploit the GALEX UV color m FUV - m NUV to cull the most promising targets for follow-up studies, with blue (red) GALEX colors indicating transparent (opaque) sight lines. Extensive Monte Carlo simulations indicate an He II detection rate of ∼60% for quasars with m FUV - m NUV ∼ em ∼ 3 to be most promising for Hubble Space Telescope follow-up, with an additional 114 quasars if we consider S/N >2 detections in the FUV. Combining the statistical properties of H I absorbers with the Sloan Digital Sky Survey (SDSS) quasar luminosity function, we predict a large all-sky population of ∼200 quasars with z em >2.7 and i ∼ 304 em ∼ em ∼ em ∼< 3.5 quasars have likely underestimated their space density by selecting intergalactic medium sight lines with an excess of strong H I absorbers.

  13. The quasar luminosity function from a variability-selected sample

    Science.gov (United States)

    Hawkins, M. R. S.; Veron, P.

    1993-01-01

    A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sign of the 'break' found in the recent UVX sample of Boyle et al. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved.

  14. The Einstein database of IPC x-ray observations of optically selected and radio-selected quasars, 1.

    Science.gov (United States)

    Wilkes, Belinda J.; Tananbaum, Harvey; Worrall, D. M.; Avni, Yoram; Oey, M. S.; Flanagan, Joan

    1994-01-01

    We present the first volume of the Einstein quasar database. The database includes estimates of the X-ray count rates, fluxes, and luminosities for 514 quasars and Seyfert 1 galaxies observed with the Imaging Proportional Counter (IPC) aboard the Einstein Observatory. All were previously known optically selected or radio-selected objects, and most were the targets of the X-ray observations. The X-ray properties of the Active Galactic Nuclei (AGNs) have been derived by reanalyzing the IPC data in a systematic manner to provide a uniform database for general use by the astronomical community. We use the database to extend earlier quasar luminosity studies which were made using only a subset of the currently available data. The database can be accessed on internet via the SAO Einstein on-line system ('Einline') and is available in ASCII format on magnetic tape and DOS diskette.

  15. SDSS QUASARS IN THE WISE PRELIMINARY DATA RELEASE AND QUASAR CANDIDATE SELECTION WITH OPTICAL/INFRARED COLORS

    International Nuclear Information System (INIS)

    Wu Xuebing; Hao Guoqiang; Jia Zhendong; Zhang Yanxia; Peng Nanbo

    2012-01-01

    We present a catalog of 37,842 quasars in the Sloan Digital Sky Survey (SDSS) Data Release 7, which have counterparts within 6'' in the Wide-field Infrared Survey Explorer (WISE) Preliminary Data Release. The overall WISE detection rate of the SDSS quasars is 86.7%, and it decreases to less than 50.0% when the quasar magnitude is fainter than i = 20.5. We derive the median color-redshift relations based on this SDSS-WISE quasar sample and apply them to estimate the photometric redshifts of the SDSS-WISE quasars. We find that by adding the WISE W1- and W2-band data to the SDSS photometry we can increase the photometric redshift reliability, defined as the percentage of sources with photometric and spectroscopic redshift difference less than 0.2, from 70.3% to 77.2%. We also obtain the samples of WISE-detected normal and late-type stars with SDSS spectroscopy, and present a criterion in the z – W1 versus g – z color-color diagram, z – W1 > 0.66(g – z) + 2.01, to separate quasars from stars. With this criterion we can recover 98.6% of 3089 radio-detected SDSS-WISE quasars with redshifts less than four and overcome the difficulty in selecting quasars with redshifts between 2.2 and 3 from SDSS photometric data alone. We also suggest another criterion involving the WISE color only, W1 – W2 > 0.57, to efficiently separate quasars with redshifts less than 3.2 from stars. In addition, we compile a catalog of 5614 SDSS quasars detected by both WISE and UKIDSS surveys and present their color-redshift relations in the optical and infrared bands. By using the SDSS ugriz, UKIDSS, YJHK, and WISE W1- and W2-band photometric data, we can efficiently select quasar candidates and increase the photometric redshift reliability up to 87.0%. We discuss the implications of our results on the future quasar surveys. An updated SDSS-WISE quasar catalog consisting of 101,853 quasars with the recently released WISE all-sky data is also provided.

  16. Quasars Probing Quasars. X. The Quasar Pair Spectral Database

    Science.gov (United States)

    Findlay, Joseph R.; Prochaska, J. Xavier; Hennawi, Joseph F.; Fumagalli, Michele; Myers, Adam D.; Bartle, Stephanie; Chehade, Ben; DiPompeo, Michael A.; Shanks, Tom; Lau, Marie Wingyee; Rubin, Kate H. R.

    2018-06-01

    The rare close projection of two quasars on the sky provides the opportunity to study the host galaxy environment of a foreground quasar in absorption against the continuum emission of a background quasar. For over a decade the “Quasars probing quasars” series has utilized this technique to further the understanding of galaxy formation and evolution in the presence of a quasar at z > 2, resolving scales as small as a galactic disk and from bound gas in the circumgalactic medium to the diffuse environs of intergalactic space. Presented here is the public release of the quasar pair spectral database utilized in these studies. In addition to projected pairs at z > 2, the database also includes quasar pair members at z useful for small-scale clustering studies. In total, the database catalogs 5627 distinct objects, with 4083 lying within 5‧ of at least one other source. A spectral library contains 3582 optical and near-infrared spectra for 3028 of the cataloged sources. As well as reporting on 54 newly discovered quasar pairs, we outline the key contributions made by this series over the last 10 years, summarize the imaging and spectroscopic data used for target selection, discuss the target selection methodologies, describe the database content, and explore some avenues for future work. Full documentation for the spectral database, including download instructions, is supplied at http://specdb.readthedocs.io/en/latest/.

  17. THE COMPOSITE SPECTRUM OF BOSS QUASARS SELECTED FOR STUDIES OF THE Ly α FOREST

    Energy Technology Data Exchange (ETDEWEB)

    Harris, David W.; Jensen, Trey W.; Bautista, Julian E.; Dawson, Kyle S.; Vivek, M.; Brownstein, Joel R.; Olmstead, Matthew D. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Suzuki, Nao [Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa, 277-8583 (Japan); Ge, Jian; Hamann, Fred; Herbst, H. [Department of Astronomy, University of Florida, Gainesville, FL 32611-2055 (United States); Jiang, Linhua [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Moran, Sarah E. [Barnard College, 3009 Broadway, New York, NY 10027 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Schneider, Donald P., E-mail: davidharris314@gmail.com [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

    2016-06-01

    The Baryon Oscillation Spectroscopic Survey (BOSS) has collected more than 150,000 2.1 ≤  z  ≤ 3.5 quasar spectra since 2009. Using this unprecedented sample, we create a composite spectrum in the rest-frame of 102,150 quasar spectra from 800–3300 Å at a signal-to-noise ratio close to 1000 per pixel (Δ v of 69 km s{sup −1}). Included in this analysis is a correction to account for flux calibration residuals in the BOSS spectrophotometry. We determine the spectral index as a function of redshift of the full sample, warp the composite spectrum to match the median spectral index, and compare the resulting spectrum to Sloan Digital Sky Survey (SDSS) photometry used in target selection. The quasar composite matches the color of the quasar population to 0.02 mag in g  −  r , 0.03 mag in r  −  i , and 0.01 mag in i  −  z over the redshift range 2.2 <  z  < 2.6. The composite spectrum deviates from the imaging photometry by 0.05 mag around z = 2.7, likely due to differences in target selection as the quasar colors become similar to the stellar locus at this redshift. Finally, we characterize the line features in the high signal-to-noise composite and identify nine faint lines not found in the previous composite spectrum from SDSS.

  18. Discovery of 16 New z  ∼ 5.5 Quasars: Filling in the Redshift Gap of Quasar Color Selection

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jinyi; Wu, Xue-Bing; Wang, Feige; Yang, Qian; Yue, Minghao; Wang, Shu; Li, Zefeng [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Fan, Xiaohui; Jiang, Linhua [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Bian, Fuyan [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); McGreer, Ian D.; Green, Richard; Ding, Jiani [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Yi, Weimin [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Dye, Simon [School of Physics and Astronomy, Nottingham University, University Park, Nottingham, NG7 2RD (United Kingdom); Lawrence, Andy [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)

    2017-04-01

    We present initial results from the first systematic survey of luminous z  ∼ 5.5 quasars. Quasars at z ∼ 5.5, the post-reionization epoch, are crucial tools to explore the evolution of intergalactic medium, quasar evolution, and the early super-massive black hole growth. However, it has been very challenging to select quasars at redshifts 5.3 ≤ z ≤ 5.7 using conventional color selections, due to their similar optical colors to late-type stars, especially M dwarfs, resulting in a glaring redshift gap in quasar redshift distributions. We develop a new selection technique for z ∼ 5.5 quasars based on optical, near-IR, and mid-IR photometric data from Sloan Digital Sky Survey (SDSS), UKIRT InfraRed Deep Sky Surveys—Large Area Survey (ULAS), VISTA Hemisphere Survey (VHS), and Wide Field Infrared Survey Explorer . From our pilot observations in the SDSS-ULAS/VHS area, we have discovered 15 new quasars at 5.3 ≤ z ≤ 5.7 and 6 new lower redshift quasars, with SDSS z band magnitude brighter than 20.5. Including other two z ∼ 5.5 quasars already published in our previous work, we now construct a uniform quasar sample at 5.3 ≤ z ≤ 5.7, with 17 quasars in a ∼4800 square degree survey area. For further application in a larger survey area, we apply our selection pipeline to do a test selection by using the new wide field J-band photometric data from a preliminary version of the UKIRT Hemisphere Survey (UHS). We successfully discover the first UHS selected z ∼ 5.5 quasar.

  19. HOT-DUST-POOR QUASARS IN MID-INFRARED AND OPTICALLY SELECTED SAMPLES

    International Nuclear Information System (INIS)

    Hao Heng; Elvis, Martin; Civano, Francesca; Lawrence, Andy

    2011-01-01

    We show that the hot-dust-poor (HDP) quasars, originally found in the X-ray-selected XMM-COSMOS type 1 active galactic nucleus (AGN) sample, are just as common in two samples selected at optical/infrared wavelengths: the Richards et al. Spitzer/SDSS sample (8.7% ± 2.2%) and the Palomar-Green-quasar-dominated sample of Elvis et al. (9.5% ± 5.0%). The properties of the HDP quasars in these two samples are consistent with the XMM-COSMOS sample, except that, at the 99% (∼ 2.5σ) significance, a larger proportion of the HDP quasars in the Spitzer/SDSS sample have weak host galaxy contributions, probably due to the selection criteria used. Either the host dust is destroyed (dynamically or by radiation) or is offset from the central black hole due to recoiling. Alternatively, the universality of HDP quasars in samples with different selection methods and the continuous distribution of dust covering factor in type 1 AGNs suggest that the range of spectral energy distributions could be related to the range of tilts in warped fueling disks, as in the model of Lawrence and Elvis, with HDP quasars having relatively small warps.

  20. Characterizing the evolution of WISE-selected obscured and unobscured quasars using HOD models.

    Science.gov (United States)

    Myers, Adam D.; DiPompeo, Michael A.; Mitra, Kaustav; Hickox, Ryan C.; Chatterjee, Suchetana; Whalen, Kelly

    2018-06-01

    Large-area imaging surveys in the infrared are now beginning to unlock the links between the activity of supermassive black holes and the cosmic evolution of dark matter halos during the significant times when black hole growth is enshrouded in dust. With data from the Wide-Field Infrared Survey Explorer (WISE) and complementary optical photometry, we construct samples of nearly half-a-million obscured and unobscured quasars around redshift 1. We study the dark matter halos of these populations using both angular autocorrelation functions and CMB lensing cross-correlations, carefully characterizing the redshift distribution of the obscured quasar sample using cross-correlations. Independent of our measurement technique, we find that obscured quasars occupy dark matter halos a few times more massive than their unobscured counterparts, despite being matched in luminosity at 12 and 22 microns. Modeling the two-point correlation function using a four-parameter Halo Occupation Distribution (HOD) formalism, we determine that purely optically selected quasars reside in dark matter halos that are about half the mass of WISE-selected obscured quasars, and that satellite fractions are somewhat larger for obscured quasars. We investigate scenarios such as merger-driven fueling and Eddington-dependent obscuration to explore what combinations of physical effects can reproduce our observed halo mass measurements. This work was, in part, supported by NASA ADAP award NNX16AN48G.

  1. On the selection of high-z quasars using LOFAR observations

    Science.gov (United States)

    Retana-Montenegro, Edwin; Röttgering, Huub

    2018-03-01

    We present a method to identify candidate quasars which combines optical/infrared color selection with radio detections from the Low Frequency ARray (LOFAR) at 150MHz. We apply this {method} in a region of 9 square degrees located in the Boötes field, with a wealth of multi-wavelength data. Our LOFAR imaging in the central region reaches a rms noise of ˜50μJy with a resolution of 5''. This is so deep that we also routinely, `radio-quiet' quasars. We use quasar spectroscopy from the literature to calculate the completeness and efficiency of our selection method. We conduct our analysis in two redshift intervals, 151% of the spectroscopic quasars, and 80% of our candidates are in the spectroscopic sample; while for objects at 2.0-1.0 sources can be detected in the WSRT-Boötes map, we find that the spectral index distribution of the 21 quasars in the resulting sample is steeper than the general LOFAR-WSRT spectral index distribution with a median of α=-0.80±0.06. As the upcoming LOFAR wide area surveys are much deeper than the traditional 1.4GHz surveys like NVSS and FIRST, this indicates that LOFAR in combination with optical and infrared will be an excellent fishing ground to obtain large samples of quasars.

  2. The Quasar Fraction in Low-Frequency Selected Complete Samples and Implications for Unified Schemes

    Science.gov (United States)

    Willott, Chris J.; Rawlings, Steve; Blundell, Katherine M.; Lacy, Mark

    2000-01-01

    Low-frequency radio surveys are ideal for selecting orientation-independent samples of extragalactic sources because the sample members are selected by virtue of their isotropic steep-spectrum extended emission. We use the new 7C Redshift Survey along with the brighter 3CRR and 6C samples to investigate the fraction of objects with observed broad emission lines - the 'quasar fraction' - as a function of redshift and of radio and narrow emission line luminosity. We find that the quasar fraction is more strongly dependent upon luminosity (both narrow line and radio) than it is on redshift. Above a narrow [OII] emission line luminosity of log(base 10) (L(sub [OII])/W) approximately > 35 [or radio luminosity log(base 10) (L(sub 151)/ W/Hz.sr) approximately > 26.5], the quasar fraction is virtually independent of redshift and luminosity; this is consistent with a simple unified scheme with an obscuring torus with a half-opening angle theta(sub trans) approximately equal 53 deg. For objects with less luminous narrow lines, the quasar fraction is lower. We show that this is not due to the difficulty of detecting lower-luminosity broad emission lines in a less luminous, but otherwise similar, quasar population. We discuss evidence which supports at least two probable physical causes for the drop in quasar fraction at low luminosity: (i) a gradual decrease in theta(sub trans) and/or a gradual increase in the fraction of lightly-reddened (0 approximately quasar luminosity; and (ii) the emergence of a distinct second population of low luminosity radio sources which, like M8T, lack a well-fed quasar nucleus and may well lack a thick obscuring torus.

  3. A Study of Quasar Selection in the Supernova Fields of the Dark Energy Survey

    International Nuclear Information System (INIS)

    Tie, S. S.; Martini, P.; Mudd, D.; Ostrovski, F.; Reed, S. L.

    2017-01-01

    In this paper, we present a study of quasar selection using the supernova fields of the Dark Energy Survey (DES). We used a quasar catalog from an overlapping portion of the SDSS Stripe 82 region to quantify the completeness and efficiency of selection methods involving color, probabilistic modeling, variability, and combinations of color/probabilistic modeling with variability. In all cases, we considered only objects that appear as point sources in the DES images. We examine color selection methods based on the Wide-field Infrared Survey Explorer (WISE) mid-IR W1-W2 color, a mixture of WISE and DES colors (g - i and i-W1), and a mixture of Vista Hemisphere Survey and DES colors (g - i and i - K). For probabilistic quasar selection, we used XDQSO, an algorithm that employs an empirical multi-wavelength flux model of quasars to assign quasar probabilities. Our variability selection uses the multi-band χ"2-probability that sources are constant in the DES Year 1 griz-band light curves. The completeness and efficiency are calculated relative to an underlying sample of point sources that are detected in the required selection bands and pass our data quality and photometric error cuts. We conduct our analyses at two magnitude limits, i 85% for both i-band magnitude limits and efficiencies of >80% to the bright limit and >60% to the faint limit; however, the giW1 and giW1+variability methods give the highest quasar surface densities. The XDQSOz method and combinations of W1W2/giW1/XDQSOz with variability are among the better selection methods when both high completeness and high efficiency are desired. We also present the OzDES Quasar Catalog of 1263 spectroscopically confirmed quasars from three years of OzDES observation in the 30 deg"2 of the DES supernova fields. Finally, the catalog includes quasars with redshifts up to z ~ 4 and brighter than i = 22 mag, although the catalog is not complete up to this magnitude limit.

  4. A large sample of Kohonen-selected SDSS quasars with weak emission lines: selection effects and statistical properties

    Science.gov (United States)

    Meusinger, H.; Balafkan, N.

    2014-08-01

    Aims: A tiny fraction of the quasar population shows remarkably weak emission lines. Several hypotheses have been developed, but the weak line quasar (WLQ) phenomenon still remains puzzling. The aim of this study was to create a sizeable sample of WLQs and WLQ-like objects and to evaluate various properties of this sample. Methods: We performed a search for WLQs in the spectroscopic data from the Sloan Digital Sky Survey Data Release 7 based on Kohonen self-organising maps for nearly 105 quasar spectra. The final sample consists of 365 quasars in the redshift range z = 0.6 - 4.2 (z¯ = 1.50 ± 0.45) and includes in particular a subsample of 46 WLQs with equivalent widths WMg iiattention was paid to selection effects. Results: The WLQs have, on average, significantly higher luminosities, Eddington ratios, and accretion rates. About half of the excess comes from a selection bias, but an intrinsic excess remains probably caused primarily by higher accretion rates. The spectral energy distribution shows a bluer continuum at rest-frame wavelengths ≳1500 Å. The variability in the optical and UV is relatively low, even taking the variability-luminosity anti-correlation into account. The percentage of radio detected quasars and of core-dominant radio sources is significantly higher than for the control sample, whereas the mean radio-loudness is lower. Conclusions: The properties of our WLQ sample can be consistently understood assuming that it consists of a mix of quasars at the beginning of a stage of increased accretion activity and of beamed radio-quiet quasars. The higher luminosities and Eddington ratios in combination with a bluer spectral energy distribution can be explained by hotter continua, i.e. higher accretion rates. If quasar activity consists of subphases with different accretion rates, a change towards a higher rate is probably accompanied by an only slow development of the broad line region. The composite WLQ spectrum can be reasonably matched by the

  5. Discovery of a Color-selected Quasar at z = 5.50.

    Science.gov (United States)

    Stern; Spinrad; Eisenhardt; Bunker; Dawson; Stanford; Elston

    2000-04-20

    We present observations of RD J030117+002025, a quasar at z=5.50 discovered from deep, multicolor, ground-based observations covering 74 arcmin2. This is the most distant quasar or active galaxy currently known. The object was targeted as an R-band dropout, with RAB>26.3 (3 sigma limit in a 3&arcsec; diameter region), IAB=23.8, and zAB=23.4. The Keck/Low-Resolution Imaging Spectrometer spectrum shows broad Lyalpha/N v lambda1240 emission and sharp absorption decrements from the highly redshifted hydrogen forests. The fractional continuum depression due to the Lyalpha forest is DA=0.90. RD J030117+002025 is the least luminous high-redshift quasar known (MB approximately -22.7).

  6. Space Density Of Optically-Selected Type II Quasars From The SDSS

    Science.gov (United States)

    Reyes, Reinabelle; Zakamska, N. L.; Strauss, M. A.; Green, J.; Krolik, J. H.; Shen, Y.; Richards, G. T.

    2007-12-01

    Type II quasars are luminous Active Galactic Nuclei (AGN) whose central regions are obscured by large amounts of gas and dust. In this poster, we present a catalog of 887 type II quasars with redshifts z<0.83 from the Sloan Digital Sky Survey (SDSS), selected based on their emission lines, and derive the 1/Vmax [OIII] 5007 luminosity function from this sample. Since some objects may not be included in the sample because they lack strong emission lines, the derived luminosity function is only a lower limit. We also derive the [OIII] 5007 luminosity function for a sample of type I (broad-line) quasars in the same redshift range. Taking [OIII] 5007 luminosity as a tracer of intrinsic luminosity in both type I and type II quasars, we obtain lower limits to the type II quasar fraction as a function of [OIII] 5007 luminosity, from L[OIII] = 108.3 to 1010 Lsun, which roughly correspond to bolometric luminosities of 1044 to 1046 erg/s.

  7. Erratum: "Space Density of Optically Selected Type 2 Quasars" (2008, AJ, 136, 2373)

    Science.gov (United States)

    Reyes, Reinabelle; Zakamska, Nadia L.; Strauss, Michael A.; Green, Joshua; Krolik, Julian H.; Shen, Yue; Richards, Gordon T.; Anderson, Scott F.; Schneider, Donald P.

    2010-03-01

    Figure 12 of the paper "Space Density of Optically Selected Type 2 Quasars" compares the obscured quasar fractions derived in our work with those of other studies. Unfortunately, some of the points from these other studies were shown incorrectly. Specifically, the results from X-ray data—Hasinger (2004; open circles) and Ueda et al. (2003; open squares)—which we had taken from Figure 16 of Hopkins et al. (2006), were affected by a luminosity conversion error, in the sense that the displayed luminosities for these data were too high by ~1 dex. With this erratum, we correct this problem and update the figure. The new version (Figure 12) shows more recent results from Hasinger (2008), in lieu of the Hasinger (2004) data points. These are based on data in the redshift range z = 0.2-3.2 (open circles) in that work. The best linear fit to these data (black dashed line) is consistent with that derived for the redshift slice z = 0.4-0.8, which overlaps with the highest redshift bin in our study, and is higher than that derived for redshifts smaller than 0.4 (corresponding to a shift of ~0.7 dex in luminosity). Figure 12 also shows estimates of the obscured quasar fraction derived from the ratio of IR to bolometric luminosities of an AGN sample at redshift z ~ 1 (Treister et al. 2008; filled triangles). Because the obscured quasar fractions derived from our analysis (colored arrows) are strict lower limits, there was already a hint in the previous version of Figure 12 that at high quasar luminosities, we find higher obscured quasar fractions than X-ray surveys. The correction and updates of Figure 12 strengthen this conclusion. At face value, our derived obscured quasar fractions are consistent with those from IR data (Treister et al. 2008; filled triangles). However, we find that they are significantly higher than those derived from X-ray surveys at L_[O\\,\\mathsc {iii]}\\gtrsim 10^{9.5}\\;L_{\\odot }, especially those from the recent analysis by Hasinger (2008). This

  8. Catalog of 3 < z < 5.5 Quasar Candidates Selected among XMM-Newton Sources and Its Spectroscopic Verification

    Energy Technology Data Exchange (ETDEWEB)

    Khorunzhev, Georgii; Sazonov, Sergey; Burenin, Rodion [High Energy Astrophysics, Space Research Institute, Russian Academy of Sciences, Moscow (Russian Federation); Eselevich, Maxim, E-mail: horge@iki.rssi.ru [Laboratory of Infrared Methods in Astrophysics, Institute of Solar-Terrestrial Physics, Russian Academy of Sciences, Irkutsk (Russian Federation)

    2017-11-13

    We have compiled a catalog of 903 quasar candidates (including known quasars) at 3 < z < 5.5 selected among X-ray sources from the XMM-Newton serendipitous survey (3XMM-DR4 catalog). We used photometric SDSS, 2MASS, and WISE data to select the objects. The surface number density of objects in our sample exceeds that in the SDSS spectroscopic quasar sample at the same redshifts by a factor of 1.5. We have performed spectroscopic observations of a subsample of new quasar candidates using a new low- and medium-resolution spectrograph at the 1.6-m AZT-33IK telescope (Mondy, Russia) and demonstrated that the purity of these candidates is about 65%. We have discovered one of the most distant (z = 5.08) X-ray selected quasars.

  9. Catalog of 3 < z < 5.5 Quasar Candidates Selected among XMM-Newton Sources and Its Spectroscopic Verification

    Directory of Open Access Journals (Sweden)

    Georgii Khorunzhev

    2017-11-01

    Full Text Available We have compiled a catalog of 903 quasar candidates (including known quasars at 3 < z < 5.5 selected among X-ray sources from the XMM-Newton serendipitous survey (3XMM-DR4 catalog. We used photometric SDSS, 2MASS, and WISE data to select the objects. The surface number density of objects in our sample exceeds that in the SDSS spectroscopic quasar sample at the same redshifts by a factor of 1.5. We have performed spectroscopic observations of a subsample of new quasar candidates using a new low- and medium-resolution spectrograph at the 1.6-m AZT-33IK telescope (Mondy, Russia and demonstrated that the purity of these candidates is about 65%. We have discovered one of the most distant (z = 5.08 X-ray selected quasars.

  10. Regional reliability of quantitative signal targeting with alternating radiofrequency (STAR) labeling of arterial regions (QUASAR).

    Science.gov (United States)

    Tatewaki, Yasuko; Higano, Shuichi; Taki, Yasuyuki; Thyreau, Benjamin; Murata, Takaki; Mugikura, Shunji; Ito, Daisuke; Takase, Kei; Takahashi, Shoki

    2014-01-01

    Quantitative signal targeting with alternating radiofrequency labeling of arterial regions (QUASAR) is a recent spin labeling technique that could improve the reliability of brain perfusion measurements. Although it is considered reliable for measuring gray matter as a whole, it has never been evaluated regionally. Here we assessed this regional reliability. Using a 3-Tesla Philips Achieva whole-body system, we scanned four times 10 healthy volunteers, in two sessions 2 weeks apart, to obtain QUASAR images. We computed perfusion images and ran a voxel-based analysis within all brain structures. We also calculated mean regional cerebral blood flow (rCBF) within regions of interest configured for each arterial territory distribution. The mean CBF over whole gray matter was 37.74 with intraclass correlation coefficient (ICC) of .70. In white matter, it was 13.94 with an ICC of .30. Voxel-wise ICC and coefficient-of-variation maps showed relatively lower reliability in watershed areas and white matter especially in deeper white matter. The absolute mean rCBF values were consistent with the ones reported from PET, as was the relatively low variability in different feeding arteries. Thus, QUASAR reliability for regional perfusion is high within gray matter, but uncertain within white matter. © 2014 The Authors. Journal of Neuroimaging published by the American Society of Neuroimaging.

  11. THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

    International Nuclear Information System (INIS)

    Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu; Ishizaki, Yoshifumi; Onoue, Masafusa; Toshikawa, Jun; Ishikawa, Shogo; Willott, Chris J.; Im, Myungshin; Shimasaku, Kazuhiro; Ouchi, Masami; Hibon, Pascale

    2015-01-01

    We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg 2 utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z B ) and (z B -z R ) colors, where z B and z R are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z R < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). We have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M 1450 = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M 1450 = –22.58 and a narrow Lyα emission with HWHM =427 km s –1 , which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6

  12. Discovery of a Color-selected Quasar at Z = 5.50

    Science.gov (United States)

    Stern, Daniel; Spinrad, Hyron; Eisenhardt, Peter; Bunker, Andrew J.; Dawson, Steve; Stanford, S. A.; Elston, Richard

    2000-04-01

    We present observations of RD J030117+002025, a quasar at z=5.50 discovered from deep, multicolor, ground-based observations covering 74 arcmin2. This is the most distant quasar or active galaxy currently known. The object was targeted as an R-band dropout, with RAB>26.3 (3 σ limit in a 3" diameter region), IAB=23.8, and zAB=23.4. The Keck/Low-Resolution Imaging Spectrometer spectrum shows broad Lyα/N V λ1240 emission and sharp absorption decrements from the highly redshifted hydrogen forests. The fractional continuum depression due to the Lyα forest is DA=0.90. RD J030117+002025 is the least luminous high-redshift quasar known (MB~-22.7). Based on observations at the W. M. Keck Observatory, Kitt Peak National Observatory, and Palomar Observatory. Keck Observatory is operated as a scientific partnership among the University of California, the California Institute of Technology, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  13. Burglar Target Selection

    Science.gov (United States)

    Townsley, Michael; Bernasco, Wim; Ruiter, Stijn; Johnson, Shane D.; White, Gentry; Baum, Scott

    2015-01-01

    Objectives: This study builds on research undertaken by Bernasco and Nieuwbeerta and explores the generalizability of a theoretically derived offender target selection model in three cross-national study regions. Methods: Taking a discrete spatial choice approach, we estimate the impact of both environment- and offender-level factors on residential burglary placement in the Netherlands, the United Kingdom, and Australia. Combining cleared burglary data from all study regions in a single statistical model, we make statistical comparisons between environments. Results: In all three study regions, the likelihood an offender selects an area for burglary is positively influenced by proximity to their home, the proportion of easily accessible targets, and the total number of targets available. Furthermore, in two of the three study regions, juvenile offenders under the legal driving age are significantly more influenced by target proximity than adult offenders. Post hoc tests indicate the magnitudes of these impacts vary significantly between study regions. Conclusions: While burglary target selection strategies are consistent with opportunity-based explanations of offending, the impact of environmental context is significant. As such, the approach undertaken in combining observations from multiple study regions may aid criminology scholars in assessing the generalizability of observed findings across multiple environments. PMID:25866418

  14. Quasar Photometric Redshifts and Candidate Selection: A New Algorithm Based on Optical and Mid-infrared Photometric Data

    Science.gov (United States)

    Yang, Qian; Wu, Xue-Bing; Fan, Xiaohui; Jiang, Linhua; McGreer, Ian; Green, Richard; Yang, Jinyi; Schindler, Jan-Torge; Wang, Feige; Zuo, Wenwen; Fu, Yuming

    2017-12-01

    We present a new algorithm to estimate quasar photometric redshifts (photo-zs), by considering the asymmetries in the relative flux distributions of quasars. The relative flux models are built with multivariate Skew-t distributions in the multidimensional space of relative fluxes as a function of redshift and magnitude. For 151,392 quasars in the SDSS, we achieve a photo-z accuracy, defined as the fraction of quasars with the difference between the photo-z z p and the spectroscopic redshift z s , | {{Δ }}z| =| {z}s-{z}p| /(1+{z}s) within 0.1, of 74%. Combining the WISE W1 and W2 infrared data with the SDSS data, the photo-z accuracy is enhanced to 87%. Using the Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-z accuracies are 79% and 72%, respectively. The prior probabilities as a function of magnitude for quasars, stars, and galaxies are calculated, respectively, based on (1) the quasar luminosity function, (2) the Milky Way synthetic simulation with the Besançon model, and (3) the Bayesian Galaxy Photometric Redshift estimation. The relative fluxes of stars are obtained with the Padova isochrones, and the relative fluxes of galaxies are modeled through galaxy templates. We test our classification method to select quasars using the DECaLS g, r, z, and WISE W1 and W2 photometry. The quasar selection completeness is higher than 70% for a wide redshift range 0.5publicly available.

  15. Quantitative structure-activity relationships of selective antagonists of glucagon receptor using QuaSAR descriptors.

    Science.gov (United States)

    Manoj Kumar, Palanivelu; Karthikeyan, Chandrabose; Hari Narayana Moorthy, Narayana Subbiah; Trivedi, Piyush

    2006-11-01

    In the present paper, quantitative structure activity relationship (QSAR) approach was applied to understand the affinity and selectivity of a novel series of triaryl imidazole derivatives towards glucagon receptor. Statistically significant and highly predictive QSARs were derived for glucagon receptor inhibition by triaryl imidazoles using QuaSAR descriptors of molecular operating environment (MOE) employing computer-assisted multiple regression procedure. The generated QSAR models revealed that factors related to hydrophobicity, molecular shape and geometry predominantly influences glucagon receptor binding affinity of the triaryl imidazoles indicating the relevance of shape specific steric interactions between the molecule and the receptor. Further, QSAR models formulated for selective inhibition of glucagon receptor over p38 mitogen activated protein (MAP) kinase of the compounds in the series highlights that the same structural features, which influence the glucagon receptor affinity, also contribute to their selective inhibition.

  16. Evolution of optically selected quasars with z<2.2 and B<20

    International Nuclear Information System (INIS)

    Marshall, H.L.

    1985-01-01

    Several complete samples of optically selected quasars are combined to give details of the quasar luminosity function and its evolution for redshifts less than 2.2. Sufficient coverage of the Hubble diagram is obtained that luminosity-dependent density evolution models can be tested and compared against pure luminosity evolution models. Although luminosity-dependent evolution is indicated if the evolution function has an exponential form, the data are consistent with a power-law evolution model that is independent of luminosity. When the sample is split into halves by redshift, a better fit is obtained with a power-law evolution model than with an exponential model. Furthermore, the luminosity function is consistent with a power-law shape whose slope is independent of redshift. Pure luminosity evolution models wherein luminosities evolve as (1+z)/sup 3.5/ and the luminosity functioin is given by dN/dLproportionalL/sup -3.6/ are consistent with these results and fit the data very well. These results suggest that the same mass supply and energy generation mechanisms apply over several decades of optical luminosity and for z<2.2

  17. X-Ray Observations of Optically Selected, Radio-quiet Quasars. I. The ASCA Results

    Science.gov (United States)

    George, I. M.; Turner, T. J.; Yaqoob, T.; Netzer, H.; Laor, A.; Mushotzky, R. F.; Nandra, K.; Takahashi, T.

    2000-03-01

    We present the result of 27 ASCA observations of 26 radio-quiet quasars (RQQs) from the Palomar-Green (PG) survey. The sample is not statistically complete, but it is reasonably representative of RQQs in the PG survey. For many of the sources, the ASCA data are presented here for the first time. All the RQQs were detected except for two objects, both of which contain broad absorption lines in the optical band. We find the variability characteristics of the sources to be consistent with Seyfert 1 galaxies. A power law offers an acceptable description of the time-averaged spectra in the 2-10 keV (quasar frame) band for all but one data set. The best-fitting values of the photon index vary from object to object over the range 1.5~=2 and dispersion σ(Γ2-10)~=0.25. The distribution of Γ2-10 is therefore similar to that observed in other RQ active galactic nuclei (AGNs) and seems to be unrelated to X-ray luminosity. No single model adequately describes the full 0.6-10 keV (observed frame) continuum of all the RQQs. Approximately 50% of the sources can be adequately described by a single power law or by a power law with only very subtle deviations. All but one of the remaining data sets were found to have convex spectra (flattening as one moves to higher energies). The exception is PG 1411+442, in which a substantial column density (NH,z~2x1023 cm-2) obscures ~98% of the continuum. We find only five (maybe six) of 14 objects with z<~0.25 to have ``soft excesses'' at energies <~1 keV, but we find no universal shape for these spectral components. The spectrum of PG 1244+026 contains a rather narrow emission feature centered at an energy ~1 keV (quasar frame). The detection rate of absorption due to ionized material in these RQQs is lower than that seen in Seyfert 1 galaxies. In part, this may be due to selection effects. However, when detected, the absorbers in the RQQs exhibit a similar range of column density and ionization parameter as Seyfert 1 galaxies. We find

  18. Eight new quasars discovered by the Guoshoujing Telescope (LAMOST) in one extragalactic field

    International Nuclear Information System (INIS)

    Wu Xuebing; Jia Zhendong; Chen Zhaoyu; Zuo Wenwen; Zhao Yongheng; Luo Ali; Bai Zhongrui; Chen Jianjun; Zhang Haotong; Yan Hongliang; Ren Juanjuan; Sun Shiwei; Wu Hong; Zhang Yong; Li Yeping; Lu Qishuai; Wang You; Ni Jijun; Wang Hai; Kong Xu

    2010-01-01

    We report the discovery of eight new quasars in one extragalactic field (a five-degree field centered at RA = 08 h 58 m 08.2 s , Dec = 01 o 32'29.7') with the Guoshoujing Telescope (LAMOST) commissioning observations made on 2009 December 18. These quasars, with i magnitudes from 16.44 to 19.34 and redshifts from 0.898 to 2.773, were not identified in the SDSS spectroscopic survey, though six of them with redshifts less than 2.5 were selected as quasar targets in SDSS. Except for one source without near-IR Y-band data, seven of these eight new quasars satisfy a newly proposed quasar selection criterion involving both near-IR and optical colors. Two of them were found in the 'redshift desert' for quasars (z from 2.2 to 3), indicating that the new criterion is efficient for uncovering missing quasars with similar optical colors to stars. Although LAMOST encountered some problems during the commissioning observations, we were still able to identify 38 other known SDSS quasars in this field, with i magnitudes from 16.24 to 19.10 and redshifts from 0.297 to 4.512. Our identifications imply that a substantial fraction of quasars may be missing in previous quasar surveys. The implication of our results to the future LAMOST quasar survey is discussed. (research papers)

  19. Quasars Probing Quasars: The Circumgalactic Medium Surrounding Z 2 Quasars

    Science.gov (United States)

    Lau, Marie Wingyee

    Models of galaxy formation make the most direct predictions on gas related processes. Specifically, a picture on how gas flows through dark matter halos and onto galaxies to fuel star formation. A major prediction is that massive halos, including those hosting the progenitors of massive elliptical galaxies, exhibit a higher fraction of hot gas with T 107 K. Another prediction is that some mechanism must be invoked to quench the supply of cool gas in massive systems. Under the current galaxy formation paradigm, every massive galaxy has undergone a quasar phase, making high-redshift quasars the progenitors of inactive supermassive black holes found in the center of nearly all galaxies. Moreover, quasars clustering implies Mhalo = 1012.5 Msun , making quasar-host galaxies the progenitors of present day, massive, red and dead galaxies. The Quasars Probing Quasars survey is well-suited to examine gas related processes in the context of massive galaxy formation, as well as quasar feedback. To date the survey has selected 700 closely projected quasar pairs. To study the circumgalactic medium, a sub-sample of pairs with projected separation within 300 kpc at the foreground quasar's redshift are selected. From the first to seventh paper in the Quasars Probing Quasars series, the statistical results had been limited to covering fractions, equivalent widths, and without precise redshift measurements of the foreground quasars. Signatures of quasar feedback in the cool circumgalactic medium had not been identified. Hence, a sub-sample of 14 pairs with echellette spectra are selected for more detailed analysis. It is found that the low and high ions roughly trace each other in velocity structure. The HI and low ion surface densities decline with projected distance. HI absorption is strong even beyond the virial radius. Unresolved Lyalpha emission in one case and NV detection in another case together imply that a fraction of transverse sightlines are illuminated. The ionization

  20. The WISSH quasars project. II. Giant star nurseries in hyper-luminous quasars

    Science.gov (United States)

    Duras, F.; Bongiorno, A.; Piconcelli, E.; Bianchi, S.; Pappalardo, C.; Valiante, R.; Bischetti, M.; Feruglio, C.; Martocchia, S.; Schneider, R.; Vietri, G.; Vignali, C.; Zappacosta, L.; La Franca, F.; Fiore, F.

    2017-08-01

    Context. Studying the coupling between the energy output produced by the central quasar and the host galaxy is fundamental to fully understand galaxy evolution. Quasar feedback is indeed supposed to dramatically affect the galaxy properties by depositing large amounts of energy and momentum into the interstellar medium (ISM). Aims: In order to gain further insights on this process, we study the spectral energy distributions (SEDs) of sources at the brightest end of the quasar luminosity function, for which the feedback mechanism is assumed to be at its maximum, given their high efficiency in driving powerful outflows. Methods: We modelled the rest-frame UV-to-far-IR SEDs of 16 WISE-SDSS Selected Hyper-luminous (WISSH) quasars at 1.8 code to account for the contribution of the quasar-related emission to the far-IR fluxes. Results: Most SEDs are well described by a standard combination of accretion disc plus torus and cold dust emission. However, about 30% of SEDs require an additional emission component in the near-IR, with temperatures peaking at 750 K, which indicates that a hotter dust component is present in these powerful quasars. We measure extreme values of both AGN bolometric luminosity (LBOL > 1047 erg/s) and star formation rate (up to 2000 M⊙/yr) based on the quasar-corrected, IR luminosity of the host galaxy. A new relation between quasar and star formation luminosity is derived (LSF ∝ L0.73QSO) by combining several Herschel-detected quasar samples from z 0 to 4. WISSH quasars have masses ( 108M⊙) and temperatures ( 50 K) of cold dust in agreement with those found for other high-z IR luminous quasars. Conclusions: Thanks to their extreme nuclear and star formation luminosities, the WISSH quasars are ideal targets to shed light on the feedback mechanism and its effect on the evolution of their host galaxies, as well as on the merger-induced scenario that is commonly assumed to explain these exceptional luminosities. Future observations will be

  1. Mass Functions of the Active Black Holes in Distant Quasars from the Large Bright Quasar Survey, the Bright Quasar Survey, and the Color-Selected Sample of the SDSS Fall Equatorial Stripe

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Osmer, Patrick S.

    2009-01-01

    We present mass functions of distant actively accreting supermassive black holes residing in luminous quasars discovered in the Large Bright Quasar Survey, the Bright Quasar Survey, and the Fall Equatorial Stripe of the Sloan Digital Sky Survey (SDSS). The quasars cover a wide range of redshifts (0...... functions at similar redshifts based on the SDSS Data Release 3 quasar catalog presented by Vestergaard et al. We see clear evidence of cosmic downsizing in the comoving space density distribution of active black holes in the LBQS sample alone. In forthcoming papers, further analysis, comparison......, and discussion of these mass functions will be made with other existing black hole mass functions, notably that based on the SDSS DR3 quasar catalog. We present the relationships used to estimate the black hole mass based on the MgII emission line; the relations are calibrated to the Hbeta and CIV relations...

  2. On the completeness of a sample of bright quasars selected by colour excess in the direction of the North Galactic Pole

    International Nuclear Information System (INIS)

    Warnock, A. III; Usher, P.D.

    1986-01-01

    The Medium Bright Quasar survey (MBQS) shows evidence for a dearth of bright quasars in a Palomar Schmidt field centred on Selected Area (SA) 57 near the North Galactic Pole, compared to similar fields centred on SA 28, 29, 55, and 94. The SA 57 field has been searched again for bright quasar candidates with the held of a second survey plate exposed according to a slightly modified Haro-Luyten three-colour (Tonantzintla) prescription. Candidates so selected have both a blue and ultraviolet excess (B-UVX). The main result of the paper is that there appear to be no B-UVX quasars in the SA 57 field that are brighter than B=17.25 mag. The significance of this apparent anomaly is briefly discussed. (author)

  3. Distribution in depth of quasars

    International Nuclear Information System (INIS)

    Schmidt, M.; Green, R.F.

    1980-01-01

    The authors discuss the distribution in depth of different kinds of quasars: quasi-stellar radio sources with steep radio spectrum, those with flat radio spectrum, and optically selected quasars. All exhibit an increase of space density with distance to a different degree. The optically selected quasars, in particular, show a steep increase of surface density with magnitude. The steepness of the increase is inconsistent with a uniform distribution of quasars in the local hypothesis. In the cosmological hypothesis the co-moving space density of optically selected quasars increases by a factor of 100,000 to a redshift of 2, and by factors of 1000 and 10 for steep-spectrum and flat-spectrum radio quasars, respectively. (Auth.)

  4. Clustering of quasars in SDSS-IV eBOSS: study of potential systematics and bias determination

    Energy Technology Data Exchange (ETDEWEB)

    Laurent, Pierre; Goff, Jean-Marc Le; Burtin, Etienne; Bourboux, Hélion du Mas des; Palanque-Delabrouille, Nathalie [IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Eftekharzadeh, Sarah; Myers, Adam [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); White, Martin [Lawrence Berkeley National Lab, 1 Cyclotron Rd, Berkeley CA 94720 (United States); Ross, Ashley J. [Center for Cosmology and AstroParticle Physics, The Ohio State University, Columbus, OH 43210 (United States); Tinker, Jeremy [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, 10003 (United States); Tojeiro, Rita [School of Physics and Astronomy, North Haugh, St. Andrews KY16 9SS (United Kingdom); Bautista, Julian; Dawson, Kyle [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Brinkmann, Jonathan [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States); Comparat, Johan [Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, 85748 Garching (Germany); Kneib, Jean-Paul [Laboratoire d' Astrophysique, École Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); McGreer, Ian D. [Steward Observatory, University of Arizona, Tucson, AZ 85721–0065 (United States); Percival, Will J. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama building, PO1 3FX, Portsmouth (United Kingdom); Prada, Francisco, E-mail: jmlegoff@cea.fr [Instituto de Fìsica Teórica (IFT) UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); and others

    2017-07-01

    We study the first year of the eBOSS quasar sample in the redshift range 0.9< z <2.2 which includes 68,772 homogeneously selected quasars. We show that the main source of systematics in the evaluation of the correlation function arises from inhomogeneities in the quasar target selection, particularly related to the extinction and depth of the imaging data used for targeting. We propose a weighting scheme that mitigates these systematics. We measure the quasar correlation function and provide the most accurate measurement to date of the quasar bias in this redshift range, b {sub Q} = 2.45 ± 0.05 at z-bar =1.55, together with its evolution with redshift. We use this information to determine the minimum mass of the halo hosting the quasars and the characteristic halo mass, which we find to be both independent of redshift within statistical error. Using a recently-measured quasar-luminosity-function we also determine the quasar duty cycle. The size of this first year sample is insufficient to detect any luminosity dependence to quasar clustering and this issue should be further studied with the final ∼500,000 eBOSS quasar sample.

  5. Testing and selecting cosmological models with ultra-compact radio quasars

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaolei [Beijing Normal University, Department of Astronomy, Beijing (China); University of Michigan, Department of Physics, Ann Arbor, MI (United States); Cao, Shuo; Qi, Jingzhao; Zhu, Zong-Hong [Beijing Normal University, Department of Astronomy, Beijing (China); Zheng, Xiaogang; Biesiada, Marek [Beijing Normal University, Department of Astronomy, Beijing (China); University of Silesia, Department of Astrophysics and Cosmology, Institute of Phyisics, Katowice (Poland)

    2017-10-15

    In this paper, we place constraints on four alternative cosmological models under the assumption of the spatial flatness of the Universe: CPL, EDE, GCG and MPC. A new compilation of 120 compact radio quasars observed by very-long-baseline interferometry, which represents a type of new cosmological standard rulers, are used to test these cosmological models. Our results show that the fits on CPL obtained from the quasar sample are well consistent with those obtained from BAO. For other cosmological models considered, quasars provide constraints in agreement with those derived with other standard probes at 1σ confidence level. Moreover, the results obtained from other statistical methods including figure of merit, Om(z) and statefinder diagnostics indicate that: (1) Radio quasar standard ruler could provide better statistical constraints than BAO for all cosmological models considered, which suggests its potential to act as a powerful complementary probe to BAO and galaxy clusters. (2) Turning to Om(z) diagnostics, CPL, GCG and EDE models cannot be distinguished from each other at the present epoch. (3) In the framework of statefinder diagnostics, MPC and EDE will deviate from the ΛCDM model in the near future, while GCG model cannot be distinguished from the ΛCDM model unless much higher precision observations are available. (orig.)

  6. THE JET POWER AND EMISSION-LINE CORRELATIONS OF RADIO-LOUD OPTICALLY SELECTED QUASARS

    International Nuclear Information System (INIS)

    Punsly, Brian; Zhang Shaohua

    2011-01-01

    In this Letter, the properties of the extended radio emission form Sloan Digital Sky Survey Data Release 7 quasars with 0.4 20-30 kpc). The frequency of quasars with FR II level extended radio emission is ∼2.3% and >0.4% of quasars have FR I level extended radio emission. The lower limit simply reflects the flux density limit of the survey. The distribution of the long-term time-averaged jet powers of these quasars, Q-bar , has a broad peak ∼3 x 10 44 erg s -1 that turns over below 10 44 erg s -1 and sources above 10 45 erg s -1 are extremely rare. It is found that the correlation between the bolometric (total thermal) luminosity of the accretion flow, L bol , and Q-bar is not strong. The correlation of Q-bar with narrow line luminosity is stronger than the correlation with broad line luminosity and the continuum luminosity. It is therefore concluded that previous interpretations of correlations of Q-bar with narrow line strengths in radio galaxies as a direct correlation of jet power and accretion power have been overstated. It is explained why this interpretation mistakenly overlooks the sizeable fraction of sources with weak accretion luminosity and powerful jets discovered by Ogle et al.

  7. THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82

    International Nuclear Information System (INIS)

    McGreer, Ian D.; Fan Xiaohui; Jiang Linhua; Richards, Gordon T.; Strauss, Michael A.; Ross, Nicholas P.; White, Martin; Shen Yue; Schneider, Donald P.; Brandt, W. Niel; Myers, Adam D.; DeGraf, Colin; Glikman, Eilat; Ge Jian; Streblyanska, Alina

    2013-01-01

    We present a measurement of the Type I quasar luminosity function at z = 5 using a large sample of spectroscopically confirmed quasars selected from optical imaging data. We measure the bright end (M 1450 2 , then extend to lower luminosities (M 1450 2 of deep, coadded imaging in the SDSS Stripe 82 region (the celestial equator in the Southern Galactic Cap). The faint sample includes 14 quasars with spectra obtained as ancillary science targets in the SDSS-III Baryon Oscillation Spectroscopic Survey, and 59 quasars observed at the MMT and Magellan telescopes. We construct a well-defined sample of 4.7 1450 * ∼-27). The bright-end slope is steep (β ∼ 1450 < –26) from z = 5 to z = 6 than from z = 4 to z = 5, suggesting a more rapid decline in quasar activity at high redshift than found in previous surveys. Our model for the quasar luminosity function predicts that quasars generate ∼30% of the ionizing photons required to keep hydrogen in the universe ionized at z = 5.

  8. A Polarimetric Search for Hidden Quasars in Three Radio-selected Ultraluminous Infrared Galaxies

    International Nuclear Information System (INIS)

    Tran, H.D.; Brotherton, M.S.; Stanford, S.A.; Breugel, W. van; Dey, A.; Stern, D.; Antonucci, R.

    1999-01-01

    We have carried out a spectropolarimetric search for hidden broad-line quasars in three ultraluminous infrared galaxies (ULIRGs) discovered in the positional correlations between sources detected in deep radio surveys and the IRAS Faint Source Catalog. Only the high-ionization Seyfert 2 galaxy TF J1736+1122 is highly polarized, displaying a broad-line spectrum visible in polarized light. The other two objects, TF J1020+6436 and FF J1614+3234, display spectra dominated by a population of young (A type) stars similar to those of open-quotes E+Aclose quotes galaxies. They are unpolarized, showing no sign of hidden broad-line regions. The presence of young starburst components in all three galaxies indicates that the ULIRG phenomenon encompasses both active galactic nuclei (AGNs) and starburst activity, but the most energetic ULIRGs do not necessarily harbor open-quotes buried quasars.close quotes We find that a luminous infrared galaxy is most likely to host an obscured quasar if it exhibits a high-ionization ([O iii] λ5007/Hβ approx-gt 5) spectrum typical of a 'classic' Seyfert 2 galaxy with little or no Balmer absorption lines, is 'ultraluminous' (L IR approx-gt 10 12 L circle-dot ), and has a 'warm' IR color (f 25 /f 60 approx-gt 0.25). The detection of hidden quasars in this group but not in the low-ionization, starburst-dominated ULIRGs (classified as LINERs or H ii galaxies) may indicate an evolutionary connection, with the latter being found in younger systems. copyright copyright 1999. The American Astronomical Society

  9. The Frequency of Intrinsic X-Ray Weakness among Broad Absorption Line Quasars

    Science.gov (United States)

    Liu, Hezhen; Luo, B.; Brandt, W. N.; Gallagher, S. C.; Garmire, G. P.

    2018-06-01

    We present combined ≈14–37 ks Chandra observations of seven z = 1.6–2.7 broad absorption line (BAL) quasars selected from the Large Bright Quasar Survey (LBQS). These seven objects are high-ionization BAL (HiBAL) quasars, and they were undetected in the Chandra hard band (2–8 keV) in previous observations. The stacking analyses of previous Chandra observations suggested that these seven objects likely contain some candidates for intrinsically X-ray weak BAL quasars. With the new Chandra observations, six targets are detected. We calculate their effective power-law photon indices and hard-band flux weakness, and find that two objects, LBQS 1203+1530 and LBQS 1442–0011, show soft/steep spectral shapes ({{{Γ }}}eff}={2.2}-0.9+0.9 and {1.9}-0.8+0.9) and significant X-ray weakness in the hard band (by factors of ≈15 and 12). We conclude that the two HiBAL quasars are good candidates for intrinsically X-ray weak BAL quasars. The mid-infrared-to-ultraviolet spectral energy distributions of the two candidates are consistent with those of typical quasars. We constrain the fraction of intrinsically X-ray weak active galactic nuclei (AGNs) among HiBAL quasars to be ≈7%–10% (2/29–3/29), and we estimate it is ≈6%–23% (2/35–8/35) among the general BAL quasar population. Such a fraction is considerably larger than that among non-BAL quasars, and we suggest that intrinsically X-ray weak quasars are preferentially observed as BAL quasars. Intrinsically X-ray weak AGNs likely comprise a small minority of the luminous type 1 AGN population, and they should not affect significantly the completeness of these AGNs found in deep X-ray surveys.

  10. Eight New Luminous z > 6 Quasars Selected via SED Model Fitting of VISTA, WISE and Dark Energy Survey Year 1 Observations

    Energy Technology Data Exchange (ETDEWEB)

    Reed, S.L.; et al.

    2017-01-17

    We present the discovery and spectroscopic confirmation with the ESO NTT and Gemini South telescopes of eight new 6.0 < z < 6.5 quasars with z$_{AB}$ < 21.0. These quasars were photometrically selected without any star-galaxy morphological criteria from 1533 deg$^{2}$ using SED model fitting to photometric data from the Dark Energy Survey (g, r, i, z, Y), the VISTA Hemisphere Survey (J, H, K) and the Wide-Field Infrared Survey Explorer (W1, W2). The photometric data was fitted with a grid of quasar model SEDs with redshift dependent Lyman-{\\alpha} forest absorption and a range of intrinsic reddening as well as a series of low mass cool star models. Candidates were ranked using on a SED-model based $\\chi^{2}$-statistic, which is extendable to other future imaging surveys (e.g. LSST, Euclid). Our spectral confirmation success rate is 100% without the need for follow-up photometric observations as used in other studies of this type. Combined with automatic removal of the main types of non-astrophysical contaminants the method allows large data sets to be processed without human intervention and without being over run by spurious false candidates. We also present a robust parametric redshift estimating technique that gives comparable accuracy to MgII and CO based redshift estimators. We find two z $\\sim$ 6.2 quasars with HII near zone sizes < 3 proper Mpc which could indicate that these quasars may be young with ages < 10$^6$ - 10$^7$ years or lie in over dense regions of the IGM. The z = 6.5 quasar VDESJ0224-4711 has J$_{AB}$ = 19.75 is the second most luminous quasar known with z > 6.5.

  11. Paired quasars near NGC 2639: Evidence for quasars in superclusters

    International Nuclear Information System (INIS)

    Ford, H.; Ciardullo, R.; Harms, R.

    1983-01-01

    Arp found 10 quasars near a low-redshift galaxy 27' SSE of NGC 2639. Six of the quasars can be grouped into three redshift pairs which align across the anonymous galaxy. The large number of quasars and pairings could show an association with the low-redshift galaxy, or alternatively, might be due to superclusters seen along the line of sight. We tested the latter hypothesis by using deep, red-sensitive Lick 3 m prime focus plates to search for a supercluster associated with the z = 0.3 quasar pair. The plates show extended nebulosity associated with the quasar U10 (thetaapprox.7'', or 20 kpc at z = 0.3) and a richness class 1, Bautz-Morgan type III cluster 4' NW of U10. A spectrum of one the cluster's brightest galaxies gives z = 0.34, suggesting that the cluster and quasar are unassociated. We obtained spectra of eight of the quasars and find that (i) two of the quasars have very strong absorption shortward of Lyα, and (ii) two of Arp's redshifts (including one which Arp considered uncertain) are incorrect. Our redshifts break two of the redshift pairs, including the pair at z = 0.3. We use the redshift distribution of optically selected quasars to argue that the third pair has no statistical significance, and conclude that there is no basis for associating the quasars with the low-redshift anonymous galaxy. The disappearance of the redshift pairs vitiates the possibility of testing the paired-quasars-in-superclusters hypothesis in the NGC 2639 field

  12. There Are (super)Giants in the Sky: Searching for Misidentified Massive Stars in Algorithmically-Selected Quasar Catalogs

    Science.gov (United States)

    Dorn-Wallenstein, Trevor Z.; Levesque, Emily

    2017-11-01

    Thanks to incredible advances in instrumentation, surveys like the Sloan Digital Sky Survey have been able to find and catalog billions of objects, ranging from local M dwarfs to distant quasars. Machine learning algorithms have greatly aided in the effort to classify these objects; however, there are regimes where these algorithms fail, where interesting oddities may be found. We present here an X-ray bright quasar misidentified as a red supergiant/X-ray binary, and a subsequent search of the SDSS quasar catalog for X-ray bright stars misidentified as quasars.

  13. The statistics of quasar-galaxy separations

    International Nuclear Information System (INIS)

    Phillips, S.

    1983-01-01

    One of the arguments put forward in favor of physical associations between low redshift galaxies and high redshift quasars is shown to be void. The argument is based on the form of the relationship for 'close' pairs of quasars and galaxies and on the size of their separations. Simple statistical reasoning based on selection effects shows that the relationship for quasar-galaxy pairs is expected if the objects are not physically associated. Further, the actual separations of the closest pairs are in close agreement with those expected given the observed numbers of nearby galaxies and the total number of known quasars. This argument avoids the controversial number density of quasars

  14. Fuzzy target selection using RFM variables

    NARCIS (Netherlands)

    Kaymak, U.

    2001-01-01

    An important data mining problem from the world of direct marketing is target selection. The main task in target selection is the determination of potential customers for a product from a client database. Target selection algorithms identify the profiles of customer groups for a particular product,

  15. Quasars as Cosmological Standard Candles

    International Nuclear Information System (INIS)

    Negrete, C. Alenka; Dultzin, Deborah; Marziani, Paola; Sulentic, Jack W.; Esparza-Arredondo, Donají; Martínez-Aldama, Mary L.; Del Olmo, Ascensión

    2017-01-01

    We propose the use of quasars with accretion rate near the Eddington ratio (extreme quasars) as standard candles. The selection criteria are based on the Eigenvector 1 (E1) formalism. Our first sample is a selection of 334 optical quasar spectra from the SDSS DR7 database with a S/N > 20. Using the E1, we define primary and secondary selection criteria in the optical spectral range. We show that it is possible to derive a redshift-independent estimate of luminosity for extreme Eddington ratio sources. Our results are consistent with concordance cosmology but we need to work with other spectral ranges to take into account the quasar orientation, among other constrains.

  16. Quasars as Cosmological Standard Candles

    Energy Technology Data Exchange (ETDEWEB)

    Negrete, C. Alenka [CONACYT Research Fellow - Instituto de Astronomía, UNAM, Mexico City (Mexico); Dultzin, Deborah [Instituto de Astronomía, UNAM, Mexico City (Mexico); Marziani, Paola [INAF, Osservatorio Astronomico di Padova, Padua (Italy); Sulentic, Jack W. [Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada (Spain); Esparza-Arredondo, Donají [Instituto de Radioastronomía y Astrofísica, Morelia (Mexico); Martínez-Aldama, Mary L.; Del Olmo, Ascensión, E-mail: alenka@astro.unam.mx [Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada (Spain)

    2017-12-15

    We propose the use of quasars with accretion rate near the Eddington ratio (extreme quasars) as standard candles. The selection criteria are based on the Eigenvector 1 (E1) formalism. Our first sample is a selection of 334 optical quasar spectra from the SDSS DR7 database with a S/N > 20. Using the E1, we define primary and secondary selection criteria in the optical spectral range. We show that it is possible to derive a redshift-independent estimate of luminosity for extreme Eddington ratio sources. Our results are consistent with concordance cosmology but we need to work with other spectral ranges to take into account the quasar orientation, among other constrains.

  17. Intergalactic dust and quasar distribution

    International Nuclear Information System (INIS)

    Soltan, A.

    1979-01-01

    Non-homogeneous intergalactic extinction may considerably affect the quasar distribution. Especially samples of quasars isolated on the basis of B-V colours are subject to this phenomenon. Apparent grouping and close pairs of quasars reported in the literature may be a result of intergalactic dust. Using surface distribution of faint blue objects selected by Hawkins and Reddish it is estimated that intergalactic extinction in B should reach approximately 1 mag out to the redshift of approximately 1. This is slightly larger than predicted by theory and comparable to the mean dust density derived from observations. (Author)

  18. NuSTAR and XMM-Newton observations of luminous, heavily obscured, WISE-selected quasars at z ∼ 2

    Energy Technology Data Exchange (ETDEWEB)

    Stern, D.; Eisenhardt, P. R. M. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Lansbury, G. B.; Alexander, D. M.; Del Moro, A.; Gandhi, P. [Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Assef, R. J. [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Brandt, W. N.; Griffith, R. L. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Baloković, M.; Bridge, C. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22 (Chile); Benford, D. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Blain, A. [Physics and Astronomy, University of Leicester, 1 University Road, Leicester, LE1 7RH (United Kingdom); Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Brightman, M. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748, Garching bei München (Germany); Christensen, F. E. [Danish Technical University, DK-2800 Lyngby (Denmark); Comastri, A., E-mail: daniel.k.stern@jpl.nasa.gov [INAF Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127, Bologna (Italy); and others

    2014-10-20

    We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected active galactic nuclei (AGNs) at z ∼ 2 across a broad X-ray band (0.1 – 79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands but bright at 12 μm (W3) and 22 μm (W4), are extremely rare, with only ∼1000 so-called 'W1W2-dropouts' across the extragalactic sky. Optical spectroscopy reveals typical redshifts of z ∼ 2 for this population, implying rest-frame mid-IR luminosities of νL {sub ν}(6 μm) ∼ 6 × 10{sup 46} erg s{sup –1} and bolometric luminosities that can exceed L {sub bol} ∼ 10{sup 14} L {sub ☉}. The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10 keV) ∼ 4 × 10{sup 45} erg s{sup –1} for typical quasar templates. These are among the most AGNs known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even at rest-frame 1.5 μm. We designed our X-ray observations to obtain robust detections for gas column densities N {sub H} ≤ 10{sup 24} cm{sup –2}. In fact, the sources prove to be fainter than these predictions. Two of the sources were observed by both NuSTAR and XMM-Newton, with neither being detected by NuSTAR (f {sub 3-24} {sub keV} ≲ 10{sup –13} erg cm{sup –2} s{sup –1}), and one being faintly detected by XMM-Newton (f {sub 0.5-10} {sub keV} ∼ 5 × 10{sup –15} erg cm{sup –2} s{sup –1}). A third source was observed only with XMM-Newton, yielding a faint detection (f {sub 0.5-10} {sub keV} ∼ 7 × 10{sup –15} erg cm{sup –2} s{sup –1}). The X-ray data imply these sources are either X-ray weak, or are heavily obscured by column densities N {sub H} ≳ 10{sup 24} cm{sup –2}. The combined X-ray and mid-IR analysis seems to favor this second possibility, implying the sources are extremely obscured, consistent with Compton

  19. NuSTAR and XMM-Newton observations of luminous, heavily obscured, WISE-selected quasars at z ∼ 2

    International Nuclear Information System (INIS)

    Stern, D.; Eisenhardt, P. R. M.; Lansbury, G. B.; Alexander, D. M.; Del Moro, A.; Gandhi, P.; Assef, R. J.; Brandt, W. N.; Griffith, R. L.; Ballantyne, D. R.; Baloković, M.; Bridge, C.; Bauer, F. E.; Benford, D.; Blain, A.; Boggs, S. E.; Craig, W. W.; Brightman, M.; Christensen, F. E.; Comastri, A.

    2014-01-01

    We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected active galactic nuclei (AGNs) at z ∼ 2 across a broad X-ray band (0.1 – 79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands but bright at 12 μm (W3) and 22 μm (W4), are extremely rare, with only ∼1000 so-called 'W1W2-dropouts' across the extragalactic sky. Optical spectroscopy reveals typical redshifts of z ∼ 2 for this population, implying rest-frame mid-IR luminosities of νL ν (6 μm) ∼ 6 × 10 46 erg s –1 and bolometric luminosities that can exceed L bol ∼ 10 14 L ☉ . The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10 keV) ∼ 4 × 10 45 erg s –1 for typical quasar templates. These are among the most AGNs known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even at rest-frame 1.5 μm. We designed our X-ray observations to obtain robust detections for gas column densities N H ≤ 10 24 cm –2 . In fact, the sources prove to be fainter than these predictions. Two of the sources were observed by both NuSTAR and XMM-Newton, with neither being detected by NuSTAR (f 3-24 keV ≲ 10 –13 erg cm –2 s –1 ), and one being faintly detected by XMM-Newton (f 0.5-10 keV ∼ 5 × 10 –15 erg cm –2 s –1 ). A third source was observed only with XMM-Newton, yielding a faint detection (f 0.5-10 keV ∼ 7 × 10 –15 erg cm –2 s –1 ). The X-ray data imply these sources are either X-ray weak, or are heavily obscured by column densities N H ≳ 10 24 cm –2 . The combined X-ray and mid-IR analysis seems to favor this second possibility, implying the sources are extremely obscured, consistent with Compton-thick, luminous quasars. The discovery of a significant population of heavily obscured, extremely luminous AGNs would not conform to the standard

  20. Data mining for gravitationally lensed quasars

    Science.gov (United States)

    Agnello, Adriano; Kelly, Brandon C.; Treu, Tommaso; Marshall, Philip J.

    2015-04-01

    Gravitationally lensed quasars are brighter than their unlensed counterparts and produce images with distinctive morphological signatures. Past searches and target-selection algorithms, in particular the Sloan Quasar Lens Search (SQLS), have relied on basic morphological criteria, which were applied to samples of bright, spectroscopically confirmed quasars. The SQLS techniques are not sufficient for searching into new surveys (e.g. DES, PS1, LSST), because spectroscopic information is not readily available and the large data volume requires higher purity in target/candidate selection. We carry out a systematic exploration of machine-learning techniques and demonstrate that a two-step strategy can be highly effective. In the first step, we use catalogue-level information (griz+WISE magnitudes, second moments) to pre-select targets, using artificial neural networks. The accepted targets are then inspected with pixel-by-pixel pattern recognition algorithms (gradient-boosted trees), to form a final set of candidates. The results from this procedure can be used to further refine the simpler SQLS algorithms, with a twofold (or threefold) gain in purity and the same (or 80 per cent) completeness at target-selection stage, or a purity of 70 per cent and a completeness of 60 per cent after the candidate-selection step. Simpler photometric searches in griz+WISE based on colour cuts would provide samples with 7 per cent purity or less. Our technique is extremely fast, as a list of candidates can be obtained from a Stage III experiment (e.g. DES catalogue/data base) in a few CPU hours. The techniques are easily extendable to Stage IV experiments like LSST with the addition of time domain information.

  1. THE MAGELLANIC QUASARS SURVEY. III. SPECTROSCOPIC CONFIRMATION OF 758 ACTIVE GALACTIC NUCLEI BEHIND THE MAGELLANIC CLOUDS

    International Nuclear Information System (INIS)

    Kozłowski, Szymon; Udalski, Andrzej; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; Pietrukowicz, P.; Skowron, J.; Onken, Christopher A.; Kochanek, Christopher S.; Meixner, M.; Bonanos, A. Z.

    2013-01-01

    The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) have been observed. The targets were selected from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on their optical variability, mid-IR, and/or X-ray properties. We spectroscopically confirmed 758 quasars (565 in the LMC and 193 in the SMC) behind the clouds, of which 94% (527 in the LMC and 186 in the SMC) are newly identified. The MQS quasars have long-term (12 yr and growing for OGLE), high-cadence light curves, enabling unprecedented variability studies of quasars. The MQS quasars also provide a dense reference grid for measuring both the internal and bulk proper motions of the clouds, and 50 quasars are bright enough (I ∼< 18 mag) for absorption studies of the interstellar/intergalactic medium of the clouds

  2. Target selection for direct marketing.

    NARCIS (Netherlands)

    Bult, Jan Roelf

    1993-01-01

    In this thesis we concentrated on the use ol direct mail for targeting potential buyers. The major characteristics that influences the success of a plomotional direct mail campaign are the of-fbr,the communication elements, the timing or sequence of these communication elements, and the list of

  3. DISCOVERING BRIGHT QUASARS AT INTERMEDIATE REDSHIFTS BASED ON OPTICAL/NEAR-INFRARED COLORS

    International Nuclear Information System (INIS)

    Wu, Xue-Bing; Zuo, Wenwen; Yang, Jinyi; Yang, Qian; Wang, Feige

    2013-01-01

    The identification of quasars at intermediate redshifts (2.2 < z < 3.5) has been inefficient in most previous quasar surveys since the optical colors of quasars are similar to those of stars. The near-IR K-band excess technique has been suggested to overcome this difficulty. Our recent study also proposed to use optical/near-IR colors for selecting z < 4 quasars. To verify the effectiveness of this method, we selected a list of 105 unidentified bright targets with i ≤ 18.5 from the quasar candidates of SDSS DR6 with both SDSS ugriz optical and UKIDSS YJHK near-IR photometric data, which satisfy our proposed Y – K/g – z criterion and have photometric redshifts between 2.2 and 3.5 estimated from the nine-band SDSS-UKIDSS data. We observed 43 targets with the BFOSC instrument on the 2.16 m optical telescope at Xinglong station of the National Astronomical Observatory of China in the spring of 2012. We spectroscopically identified 36 targets as quasars with redshifts between 2.1 and 3.4. The high success rate of discovering these quasars in the SDSS spectroscopic surveyed area further demonstrates the robustness of both the Y – K/g – z selection criterion and the photometric redshift estimation technique. We also used the above criterion to investigate the possible stellar contamination rate among the quasar candidates of SDSS DR6, and found that the rate is much higher when selecting 3 < z < 3.5 quasar candidates than when selecting lower redshift candidates (z < 2.2). The significant improvement in the photometric redshift estimation when using the nine-band SDSS-UKIDSS data over the five-band SDSS data is demonstrated and a catalog of 7727 unidentified quasar candidates in SDSS DR6 selected with optical/near-IR colors and having photometric redshifts between 2.2 and 3.5 is provided. We also tested the Y – K/g – z selection criterion with the recently released SDSS-III/DR9 quasar catalog and found that 96.2% of 17,999 DR9 quasars with UKIDSS Y- and K

  4. Relativistic beaming and quasar statistics

    International Nuclear Information System (INIS)

    Orr, M.J.L.; Browne, I.W.A.

    1982-01-01

    The statistical predictions of a unified scheme for the radio emission from quasars are explored. This scheme attributes the observed differences between flat- and steep-spectrum quasars to projection and the effects of relativistic beaming of the emission from the nuclear components. We use a simple quasar model consisting of a compact relativistically beamed core with spectral index zero and unbeamed lobes, spectral index - 1, to predict the proportion of flat-spectrum sources in flux-limited samples selected at different frequencies. In our model this fraction depends on the core Lorentz factor, γ and we find that a value of approximately 5 gives satisfactory agreement with observation. In a similar way the model is used to construct the expected number/flux density counts for flat-spectrum quasars from the observed steep-spectrum counts. Again, good agreement with the observations is obtained if the average core Lorentz factor is about 5. Independent estimates of γ from observations of superluminal motion in quasars are of the same order of magnitude. We conclude that the statistical properties of quasars are entirely consistent with the predictions of simple relativistic-beam models. (author)

  5. First observation of a quasar with a redshift of 4

    International Nuclear Information System (INIS)

    Warren, S.J.; Hewett, P.C.; Irwin, M.J.; McMahon, R.G.; Bridgeland, M.T.; Bunclark, P.S.; Kibblewhite, E.J.

    1987-01-01

    The authors report the discovery of a quasar (0046-293) with a redshift z = 4.01 and another (0044-276) with a redshift z 3.42. The redshift of the former quasar is the highest yet detected and compares with the z = 3.80 of the previous most distant known quasar. The new quasars lie in the same field as three other known high-redshift quasars and were identified in a preliminary analysis of new multi-colour data derived from measurements of direct photographic plates taken with the United Kingdom Schmidt Telescope. The two new quasars are significantly fainter (msub(R) > 19) than previously known high-redshift quasars discovered by optical techniques, and demonstrate that the luminosity function of optically selected high-redshift quasars extends over at least two magnitudes. (author)

  6. Quasars Probing Quasars: the Circumgalactic Medium Surrounding z ~ 2 Quasars

    Science.gov (United States)

    Lau, Marie; Quasars Probing Quasars survey

    2018-01-01

    Understanding the circumgalactic medium--the gaseous halo surrounding a galaxy, is an integral part to understanding galaxy evolution. The z ~ 2-3 universe is interesting as this is when the star formation rate and AGN activity peak. My thesis concludes the decade-long Quasars Probing Quasars survey designed for studying massive galaxy formation and quasar feedback. I use background quasar sightlines that pass close to foreground quasars to study the circumgalactic medium of quasar-host galaxies in absorption. My sample of 149 quasar pairs involve spectra taken with 17 different optical and near IR instruments. I present results on the statistical and physical properties of the circumgalactic medium. The circumgalactic medium is enriched even beyond the virial radius. The alpha/Fe abundance ratio is enhanced, suggesting enrichment from core-collapse supernovae. The cool gas mass within the virial radius is enough to fuel star formation for another Gyr, and may account for 1/3 of the baryonic budget of the galaxy halo. The ionization state increases with projected distance from the quasar, which implies the quasar does not dominate the ionizing radiation flux. However, detection of fluorescent Lyman-alpha emission and NV absorption imply these transverse absorbers are partially illuminated by the quasar. In one peculiar case, the absorbing clump has density >100 cm^-3 and sub-parsec size. The average absorption in the circumgalactic medium exhibits large velocity widths, and is asymmetric about the systemic redshift of the galaxies. The widths are consistent with gravitational motions and Hubble flow, and outflows are not required to explain them. The asymmetry can be explained if the ionizing radiation from the quasar is anisotropic or intermittent and the gas is not in inflow. My results pose challenges for cosmological hydrodynamic simulations to produce a substantial cool gas reservoir surrounding quasars, that is also enriched and shows extreme kinematics.

  7. On the periodicity in the distribution of quasar redshifts

    International Nuclear Information System (INIS)

    Kjaergaard, P.

    1978-01-01

    The periodicity in the distribution of quasar redshifts is explained in terms of selection effects. Special attention is drawn to a selection effect caused by the redshift dependent influence of the strong emission lines on the limiting magnitude for detecting quasars. This is especially important since the number of quasars increases with a large factor per magnitude. The limiting magnitude effect applies both to spectroscopic and to UV-excess surveys. It is shown that the redshift distribution of quasars selected by a combination of UV-excess information and agreement between radio and optical position is intermediate between the redshift distribution of the two groups of quasars selected by one of the two criteria. It is also shown that the distribution of redshifts for UV-excess selected quasars is very similar to the variation of the ultrsviolet excess as a function of redshift. This evidence indicates that strong selection effects are in play. (Auth.)

  8. The FIRST-2MASS Red Quasar Survey

    International Nuclear Information System (INIS)

    Glikman, E; Helfand, D J; White, R L; Becker, R H; Gregg, M D; Lacy, M

    2007-01-01

    Combining radio observations with optical and infrared color selection--demonstrated in our pilot study to be an efficient selection algorithm for finding red quasars--we have obtained optical and infrared spectroscopy for 120 objects in a complete sample of 156 candidates from a sky area of 2716 square degrees. Consistent with our initial results, we find our selection criteria--J-K > 1.7,R-K > 4.0--yield a ∼ 50% success rate for discovering quasars substantially redder than those found in optical surveys. Comparison with UVX- and optical color-selected samples shows that ∼> 10% of the quasars are missed in a magnitude-limited survey. Simultaneous two-frequency radio observations for part of the sample indicate that a synchrotron continuum component is ruled out as a significant contributor to reddening the quasars spectra. We go on to estimate extinctions for our objects assuming their red colors are caused by dust. Continuum fits and Balmer decrements suggest E(B-V) values ranging from near zero to 2.5 magnitudes. Correcting the K-band magnitudes for these extinctions, we find that for K (le) 14.0, red quasars make up between 25% and 60% of the underlying quasar population; owing to the incompleteness of the 2MASS survey at fainter K-band magnitudes, we can only set a lower limit to the radio-detected red quasar population of > 20-30%

  9. GBT Detection of Polarization-Dependent HI Absorption and HI Outflows in Local ULIRGs and Quasars

    Science.gov (United States)

    Teng, Stacy H.; Veilleux, Sylvain; Baker, Andrew J.

    2013-01-01

    We present the results of a 21-cm HI survey of 27 local massive gas-rich late-stage mergers and merger remnants with the Green Bank Telescope (GBT). These remnants were selected from the Quasar/ULIRG Evolution Study (QUEST) sample of ultraluminous infrared galaxies (ULIRGs; L(sub 8 - 1000 micron) > 10(exp 12) solar L) and quasars; our targets are all bolometrically dominated by active galactic nuclei (AGN) and sample the later phases of the proposed ULIRG-to-quasar evolutionary sequence. We find the prevalence of HI absorption (emission) to be 100% (29%) in ULIRGs with HI detections, 100% (88%) in FIR-strong quasars, and 63% (100%) in FIR-weak quasars. The absorption features are associated with powerful neutral outflows that change from being mainly driven by star formation in ULIRGs to being driven by the AGN in the quasars. These outflows have velocities that exceed 1500 km/s in some cases. Unexpectedly, we find polarization-dependent HI absorption in 57% of our spectra (88% and 63% of the FIR-strong and FIR-weak quasars, respectively). We attribute this result to absorption of polarized continuum emission from these sources by foreground HI clouds. About 60% of the quasars displaying polarized spectra are radio-loud, far higher than the approx 10% observed in the general AGN population. This discrepancy suggests that radio jets play an important role in shaping the environments in these galaxies. These systems may represent a transition phase in the evolution of gas-rich mergers into "mature" radio galaxies.

  10. Star Formation in Dusty Quasars

    Science.gov (United States)

    Lumsden, Stuart; Croom, Scott

    2012-04-01

    Quasar mode feedback is thought to be a crucial ingredient in galaxy formation for luminous merging and star-bursting systems at high redshift. The energy from the active nucleus should cause significant gas outflows, reducing the available free gas reservoir for future star formation. It is currently unknown which observational state best corresponds to the stage at which this "blowout" should occur. We intend to test one possible source population for this transition phase, by studying the molecular gas content in a small, statistically complete sample of 3 K-band selected reddened quasars from the AUS survey. All lie in the redshift range 2quasar activity in typical galaxies, where we also expect the bulk of the stars for form as well.

  11. Quasars and galactic evolution

    CERN Document Server

    Woltjer, L

    1978-01-01

    The evolution of quasars is discussed. It is noted that substantial clustering may be present at faint magnitudes. The relationship between quasar evolution and galactic evolution is considered. (4 refs).

  12. Target-selected mutagenesis of the rat

    NARCIS (Netherlands)

    Smits, B.M.; Mudde, J.B.; Plasterk, R.; Cuppen, E.

    2004-01-01

    The rat is one of the most extensively studied model organisms, and with its genome being sequenced, tools to manipulate gene function in vivo have become increasingly important. We here report proof of principle for target-selected mutagenesis as a reverse genetic or knockout approach for the rat.

  13. Target selection for the HRIBF Project

    International Nuclear Information System (INIS)

    Dellwo, J.; Alton, G.D.; Batchelder, J.C.

    1994-01-01

    Experiments are in progress at the Oak Ridge National Laboratory (ORNL) which are designed to select the most appropriate target materials for generating particular radioactive ion beams for the Holifield Radioactive Ion Beam Facility (HRIBF). The 25-MV tandem accelerator is used to implant stable complements of interesting radioactive elements into refractory targets mounted in a high-temperature FEBIAD ion source which is on-line at the UNISOR facility. These experiments permit selection of the target material most appropriate for the rapid release of the element of interest, as well as realistic estimates of the efficiency of the FEBIAD source. From diffusion release data information on the release times and diffusion coefficients can be derived. Diffusion coefficients for CI implanted into and diffused from CeS and Zr 5 Si 3 and As, Br, and Se implanted into and diffused from Zr 5 Ge 3 have been derived from the resulting intensity versus time profiles

  14. PHOTOMETRIC OBSERVATIONS OF SELECTED, OPTICALLY BRIGHT QUASARS FOR SPACE INTERFEROMETRY MISSION AND OTHER FUTURE CELESTIAL REFERENCE FRAMES

    International Nuclear Information System (INIS)

    Ojha, Roopesh; Zacharias, Norbert; Hennessy, Gregory S.; Gaume, Ralph A.; Johnston, Kenneth J.

    2009-01-01

    Photometric observations of 235 extragalactic objects that are potential targets for the Space Interferometry Mission (SIM) are presented. Mean B, V, R, I magnitudes at the 5% level are obtained at 1-4 epochs between 2005 and 2007 using the 1 m telescopes at Cerro Tololo Inter-American Observatory and the Naval Observatory Flagstaff Station. Of the 134 sources that have V magnitudes in the Veron and Veron-Cetty catalog, a difference of over 1.0 mag is found for the observed-catalog magnitudes for about 36% of the common sources, and 10 sources show over 3 mag difference. Our first set of observations presented here form the basis of a long-term photometric variability study of the selected reference frame sources to assist in mission target selection and to support QSO multicolor photometric variability studies in general.

  15. What are quasars. 3. ed.

    International Nuclear Information System (INIS)

    Dautcourt, G.

    1982-01-01

    The subject is covered under the following headings: gigantic explosions in galaxies, the puzzle of far radio sources, all records are broken, the quasar light - a messenger from the far past, the radio mantle of quasars, where do spectral lines originate, mysterious absorption, restless quasars, quasars as infrared sources, what is the gist of the matter, was Einstein wrong, when is a quasar no quasar, quasars and cosmology, youthful escapades of a galaxy, and once again the red shift

  16. Structural Implications for Selective Targeting of PARPs.

    Science.gov (United States)

    Steffen, Jamin D; Brody, Jonathan R; Armen, Roger S; Pascal, John M

    2013-12-20

    Poly(ADP-ribose) polymerases (PARPs) are a family of enzymes that use NAD(+) as a substrate to synthesize polymers of ADP-ribose (PAR) as post-translational modifications of proteins. PARPs have important cellular roles that include preserving genomic integrity, telomere maintenance, transcriptional regulation, and cell fate determination. The diverse biological roles of PARPs have made them attractive therapeutic targets, which have fueled the pursuit of small molecule PARP inhibitors. The design of PARP inhibitors has matured over the past several years resulting in several lead candidates in clinical trials. PARP inhibitors are mainly used in clinical trials to treat cancer, particularly as sensitizing agents in combination with traditional chemotherapy to reduce side effects. An exciting aspect of PARP inhibitors is that they are also used to selectivity kill tumors with deficiencies in DNA repair proteins (e.g., BRCA1/2) through an approach termed "synthetic lethality." In the midst of the tremendous efforts that have brought PARP inhibitors to the forefront of modern chemotherapy, most clinically used PARP inhibitors bind to conserved regions that permits cross-selectivity with other PARPs containing homologous catalytic domains. Thus, the differences between therapeutic effects and adverse effects stemming from pan-PARP inhibition compared to selective inhibition are not well understood. In this review, we discuss current literature that has found ways to gain selectivity for one PARP over another. We furthermore provide insights into targeting other domains that make up PARPs, and how new classes of drugs that target these domains could provide a high degree of selectivity by affecting specific cellular functions. A clear understanding of the inhibition profiles of PARP inhibitors will not only enhance our understanding of the biology of individual PARPs, but may provide improved therapeutic options for patients.

  17. Weak hard X-ray emission from broad absorption line quasars: evidence for intrinsic X-ray weakness

    International Nuclear Information System (INIS)

    Luo, B.; Brandt, W. N.; Scott, A. E.; Alexander, D. M.; Gandhi, P.; Stern, D.; Teng, S. H.; Arévalo, P.; Bauer, F. E.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Farrah, D.; Hailey, C. J.; Harrison, F. A.; Koss, M.; Ogle, P.; Puccetti, S.; Saez, C.

    2014-01-01

    We report NuSTAR observations of a sample of six X-ray weak broad absorption line (BAL) quasars. These targets, at z = 0.148-1.223, are among the optically brightest and most luminous BAL quasars known at z < 1.3. However, their rest-frame ≈2 keV luminosities are 14 to >330 times weaker than expected for typical quasars. Our results from a pilot NuSTAR study of two low-redshift BAL quasars, a Chandra stacking analysis of a sample of high-redshift BAL quasars, and a NuSTAR spectral analysis of the local BAL quasar Mrk 231 have already suggested the existence of intrinsically X-ray weak BAL quasars, i.e., quasars not emitting X-rays at the level expected from their optical/UV emission. The aim of the current program is to extend the search for such extraordinary objects. Three of the six new targets are weakly detected by NuSTAR with ≲ 45 counts in the 3-24 keV band, and the other three are not detected. The hard X-ray (8-24 keV) weakness observed by NuSTAR requires Compton-thick absorption if these objects have nominal underlying X-ray emission. However, a soft stacked effective photon index (Γ eff ≈ 1.8) for this sample disfavors Compton-thick absorption in general. The uniform hard X-ray weakness observed by NuSTAR for this and the pilot samples selected with <10 keV weakness also suggests that the X-ray weakness is intrinsic in at least some of the targets. We conclude that the NuSTAR observations have likely discovered a significant population (≳ 33%) of intrinsically X-ray weak objects among the BAL quasars with significantly weak <10 keV emission. We suggest that intrinsically X-ray weak quasars might be preferentially observed as BAL quasars.

  18. What BOSS has taught us about Quasars.

    Science.gov (United States)

    Ross, Nicholas; SDSS-III BOSS Quasar Science Working Group

    2015-01-01

    This talk presents science highlights from the SDSS-III BOSS Quasar Survey, which has obtained spectra for over 300,000 quasars, 200,000 of which are at redshift z>2. Using this dataset, new measurements of the luminosity function have been made, with the faint end of the luminosity function now measured to z~5. New clustering results from DR12 are presented, and the weak luminosity dependence of quasar clustering at z~0.5 is also discussed.New studies of the broad absorption line (BAL) quasar population have also been performed, with a sample of BAL quasars from the original SDSS being re-observed. These new data have shown the disappearance of CIV BAL troughs and indeed the transformation of BAL QSOs to non-BAL QSOs. BAL disappearance, and emergence, events appear to be extremes of general BAL variability, and have shed light on accretion-disk wind models.We highlight the discovery of new classes of quasars including: a population of broad-line Mg II emitters found in a passive galaxy sample; objects with extremely red optical-to-mid infrared colors; objects with very curious UV line (LyA:NV) ratios and potentially the long-sought after high-redshift Type 2 Quasar population.Finally, we describe two new dedicated programs, one focusing on reverberation mapping, the other on X-ray selected quasars.A full list of papers connected to the BOSS Quasar Survey is given at: http://www.sdss3.org/science/publications.php

  19. HER2 overexpression and amplification as a potential therapeutic target in colorectal cancer: analysis of 3256 patients enrolled in the QUASAR, FOCUS and PICCOLO colorectal cancer trials.

    Science.gov (United States)

    Richman, Susan D; Southward, Katie; Chambers, Philip; Cross, Debra; Barrett, Jennifer; Hemmings, Gemma; Taylor, Morag; Wood, Henry; Hutchins, Gordon; Foster, Joseph M; Oumie, Assa; Spink, Karen G; Brown, Sarah R; Jones, Marc; Kerr, David; Handley, Kelly; Gray, Richard; Seymour, Matthew; Quirke, Philip

    2016-03-01

    HER2 overexpression/amplification is linked to trastuzumab response in breast/gastric cancers. One suggested anti-EGFR resistance mechanism in colorectal cancer (CRC) is aberrant MEK-AKT pathway activation through HER2 up-regulation. We assessed HER2-amplification/overexpression in stage II-III and IV CRC patients, assessing relationships to KRAS/BRAF and outcome. Pathological material was obtained from 1914 patients in the QUASAR stage II-III trial and 1342 patients in stage IV trials (FOCUS and PICCOLO). Tissue microarrays were created for HER2 immunohistochemistry. HER2-amplification was assessed using FISH and copy number variation. KRAS/BRAF mutation status was assessed by pyrosequencing. Progression-free survival (PFS) and overall survival (OS) data were obtained for FOCUS/PICCOLO and recurrence and mortality for QUASAR; 29/1342 (2.2%) stage IV and 25/1914 (1.3%) stage II-III tumours showed HER2 protein overexpression. Of the HER2-overexpressing cases, 27/28 (96.4%) stage IV tumours and 20/24 (83.3%) stage II-III tumours demonstrated HER2 amplification by FISH; 41/47 (87.2%) also showed copy number gains. HER2-overexpression was associated with KRAS/BRAF wild-type (WT) status at all stages: in 5.2% WT versus 1.0% mutated tumours (p < 0.0001) in stage IV and 2.1% versus 0.2% in stage II-III tumours (p = 0.01), respectively. HER2 was not associated with OS or PFS. At stage II-III, there was no significant correlation between HER2 overexpression and 5FU/FA response. A higher proportion of HER2-overexpressing cases experienced recurrence, but the difference was not significant. HER2-amplification/overexpression is identifiable by immunohistochemistry, occurring infrequently in stage II-III CRC, rising in stage IV and further in KRAS/BRAF WT tumours. The value of HER2-targeted therapy in patients with HER2-amplified CRC must be tested in a clinical trial. © 2015 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society

  20. Quasars and superclusters

    International Nuclear Information System (INIS)

    Osmer, P.S.

    1983-01-01

    The evidence for quasar superclusters is discussed, together with implications and survey techniques. The data base of clusters of pairs of quasars with similar redshifts, which is supportive of theories of gravitational lenses, indicates that quasar superclusters do exist. Surveys of large redshift quasars have shown that the quasars do not necessarily cluster. It is cautioned that randomness in an observational scheme, followed by assumptions of uniformity in analyses, will produce results that support a uniformity that may not exist. It is suggested that clusters observed in one survey should be sought in other direction using the same techniques. Continuing expanded surveys of large redshift quasars are recommended in order to form an all-sky distribution of the objects. 18 references

  1. A color hierarchy for automatic target selection.

    Directory of Open Access Journals (Sweden)

    Illia Tchernikov

    Full Text Available Visual processing of color starts at the cones in the retina and continues through ventral stream visual areas, called the parvocellular pathway. Motion processing also starts in the retina but continues through dorsal stream visual areas, called the magnocellular system. Color and motion processing are functionally and anatomically discrete. Previously, motion processing areas MT and MST have been shown to have no color selectivity to a moving stimulus; the neurons were colorblind whenever color was presented along with motion. This occurs when the stimuli are luminance-defined versus the background and is considered achromatic motion processing. Is motion processing independent of color processing? We find that motion processing is intrinsically modulated by color. Color modulated smooth pursuit eye movements produced upon saccading to an aperture containing a surface of coherently moving dots upon a black background. Furthermore, when two surfaces that differed in color were present, one surface was automatically selected based upon a color hierarchy. The strength of that selection depended upon the distance between the two colors in color space. A quantifiable color hierarchy for automatic target selection has wide-ranging implications from sports to advertising to human-computer interfaces.

  2. An astrophysics data program investigation of a synoptic study of quasar continua

    Science.gov (United States)

    Elvis, Martin

    1991-01-01

    A summary of the program is presented. The major product of the program, an atlas of quasar energy distributions, is presented in the appendices along with papers written as a result of this research. The topics covered in the papers include: (1) accurate galactic N(sub h) values toward quasars and active galactic nuclei (AGN); (2) weak bump quasars; (3) millimeter measurements of hard x ray selected active galaxies- implications for the nature of the continuous spectrum; (3) persistence and change in the soft x ray spectrum of the quasar PG1211+143; (4) the soft x ray excess in einstein quasar spectra; and (5) EXOSAT x ray spectra of quasars.

  3. GREEN BANK TELESCOPE DETECTION OF POLARIZATION-DEPENDENT H I ABSORPTION AND H I OUTFLOWS IN LOCAL ULIRGs AND QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Stacy H. [Observational Cosmology Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Veilleux, Sylvain [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Baker, Andrew J., E-mail: stacy.h.teng@nasa.gov [Department of Physics and Astronomy, Rutgers, State University of New Jersey, Piscataway, NJ 08854 (United States)

    2013-03-10

    We present the results of a 21 cm H I survey of 27 local massive gas-rich late-stage mergers and merger remnants with the Robert C. Byrd Green Bank Telescope. These remnants were selected from the Quasar/ULIRG Evolution Study sample of ultraluminous infrared galaxies (ULIRGs; L{sub 8{sub -{sub 1000{sub {mu}m}}}} > 10{sup 12} L{sub Sun }) and quasars; our targets are all bolometrically dominated by active galactic nuclei (AGNs) and sample the later phases of the proposed ULIRG-to-quasar evolutionary sequence. We find the prevalence of H I absorption (emission) to be 100% (29%) in ULIRGs with H I detections, 100% (88%) in FIR-strong quasars, and 63% (100%) in FIR-weak quasars. The absorption features are associated with powerful neutral outflows that change from being mainly driven by star formation in ULIRGs to being driven by the AGN in the quasars. These outflows have velocities that exceed 1500 km s{sup -1} in some cases. Unexpectedly, we find polarization-dependent H I absorption in 57% of our spectra (88% and 63% of the FIR-strong and FIR-weak quasars, respectively). We attribute this result to absorption of polarized continuum emission from these sources by foreground H I clouds. About 60% of the quasars displaying polarized spectra are radio-loud, far higher than the {approx}10% observed in the general AGN population. This discrepancy suggests that radio jets play an important role in shaping the environments in these galaxies. These systems may represent a transition phase in the evolution of gas-rich mergers into ''mature'' radio galaxies.

  4. Radio-continuum emission from quasar host galaxies

    International Nuclear Information System (INIS)

    Condon, J. J.; Gower, A. C.; Hutchings, J. B.; Victoria Univ., Canada; Dominion Astrophysical Observatory, Victoria)

    1987-01-01

    Seven low-redshift quasars that are likely to be in spiral galaxies have been observed in a search for radio-continuum emission from the host galaxies of quasars. The properties of the individual quasars are listed, and 1.49 GHz contour maps of the seven quasar fields are presented. Map parameters and radio source parameters are given along with optical images of three of the objects. The results indicate that these quasars probably do reside in spiral galaxies. The radio luminosities, sizes, orientations, and u values all indicate that relativistic beaming alone cannot be used to explain the differences between the present sources and the far stronger radio sources seen in blazars or larger optically selected quasar samples. However, an apparent correlation between the radio luminosity and the ratio of the optical nuclear to host-galaxy luminosity is consistent with some beaming of nuclear radiation. 26 references

  5. Overdensity of galaxies in the environment of quasar pairs

    Science.gov (United States)

    Sandrinelli, A.; Falomo, R.; Treves, A.; Scarpa, R.; Uslenghi, M.

    2018-03-01

    We report on a study of the galaxy environments of low redshift physical quasars pairs. We selected 20 pairs having projected separation Survey images, we evaluated the galaxy overdensity around these quasars in pairs and then compare it with that of a sample of isolated quasars with same redshift and luminosity. It is found that on average there is a systematic larger overdensity of galaxies around quasars in pairs with respect to that of isolated quasars. This may represent a significant link between nuclear activity and galaxy environment. However, at odds with that, the closest quasar pairs seem to inhabit poorer environments. Implications of present results and perspectives for future work are briefly discussed.

  6. Gravitational lensing of quasars

    CERN Document Server

    Eigenbrod, Alexander

    2013-01-01

    The universe, in all its richness, diversity and complexity, is populated by a myriad of intriguing celestial objects. Among the most exotic of them are gravitationally lensed quasars. A quasar is an extremely bright nucleus of a galaxy, and when such an object is gravitationally lensed, multiple images of the quasar are produced – this phenomenon of cosmic mirage can provide invaluable insights on burning questions, such as the nature of dark matter and dark energy. After presenting the basics of modern cosmology, the book describes active galactic nuclei, the theory of gravitational lensing, and presents a particular numerical technique to improve the resolution of astronomical data. The book then enters the heart of the subject with the description of important applications of gravitational lensing of quasars, such as the measurement of the famous Hubble constant, the determination of the dark matter distribution in galaxies, and the observation of the mysterious inner parts of quasars with much higher r...

  7. Radio structure in quasars

    International Nuclear Information System (INIS)

    Barthel, P.D.

    1984-01-01

    In this thesis, observational attention is given to the extended extragalactic radio sources associated with quasars. The isolated compact radio sources, often identified with quasars, are only included in the discussions. Three aspects of the radio structure in quasars and their cosmic evolution are considered: a study of the parsec scale morphology in quasar cores, in relation to the extended morphologies; an investigation of possible epoch dependent hotspot properties as well as a more detailed investigation of this fine scale structure; a VLA project was carried out to obtain morphological information on scales of 0.5 arcsec on high redshift quasars and to investigate possible epoch dependent morphological properties. MERLIN observations at 0.1 arcsec resolution to supplement the VLA data were initiated. (Auth.)

  8. A CONSTRAINT ON QUASAR CLUSTERING AT z = 5 FROM A BINARY QUASAR

    International Nuclear Information System (INIS)

    McGreer, Ian D.; Fan, Xiaohui; Eftekharzadeh, Sarah; Myers, Adam D.

    2016-01-01

    We report the discovery of a quasar pair at z = 5 separated by 21″. Both objects were identified as quasar candidates using simple color selection techniques applied to photometric catalogs from the Canada–France–Hawaii Telescope (CFHT) Legacy Survey (CFHTLS). Spectra obtained with the MMT present no discernible offset in redshift between the two objects; on the other hand, there are clear differences in the emission line profiles and in the multiwavelength spectral energy distributions that strongly disfavor the hypothesis that they are gravitationally lensed images of a single quasar. Both quasars are surprisingly bright given their proximity (a projected separation of ∼135 kpc), with i = 19.4 and i = 21.4. Previous measurements of the luminosity function demonstrate that luminous quasars are extremely rare at z = 5; the existence of this pair suggests that quasars have strong small-scale clustering at high redshift. Assuming a real-space correlation function of the form ξ(r) ∝ (r/r 0 ) −2 , this discovery implies a correlation length of r 0 ≳ 20h −1 Mpc, consistent with a rapid strengthening of quasar clustering at high redshift as seen in previous observations and predicted by theoretical models where feedback effects are inefficient at shutting down black hole growth at high redshift

  9. A CONSTRAINT ON QUASAR CLUSTERING AT z = 5 FROM A BINARY QUASAR

    Energy Technology Data Exchange (ETDEWEB)

    McGreer, Ian D.; Fan, Xiaohui [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Eftekharzadeh, Sarah; Myers, Adam D., E-mail: imcgreer@as.arizona.edu [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States)

    2016-03-15

    We report the discovery of a quasar pair at z = 5 separated by 21″. Both objects were identified as quasar candidates using simple color selection techniques applied to photometric catalogs from the Canada–France–Hawaii Telescope (CFHT) Legacy Survey (CFHTLS). Spectra obtained with the MMT present no discernible offset in redshift between the two objects; on the other hand, there are clear differences in the emission line profiles and in the multiwavelength spectral energy distributions that strongly disfavor the hypothesis that they are gravitationally lensed images of a single quasar. Both quasars are surprisingly bright given their proximity (a projected separation of ∼135 kpc), with i = 19.4 and i = 21.4. Previous measurements of the luminosity function demonstrate that luminous quasars are extremely rare at z = 5; the existence of this pair suggests that quasars have strong small-scale clustering at high redshift. Assuming a real-space correlation function of the form ξ(r) ∝ (r/r{sub 0}){sup −2}, this discovery implies a correlation length of r{sub 0} ≳ 20h{sup −1} Mpc, consistent with a rapid strengthening of quasar clustering at high redshift as seen in previous observations and predicted by theoretical models where feedback effects are inefficient at shutting down black hole growth at high redshift.

  10. X-ray Spectral Survey of WGACAT Quasars, II: Optical and Radio Properties of Quasars with Low Energy X-ray Cut-offs

    OpenAIRE

    Elvis, Martin; Fiore, Fabrizio; Giommi, Paolo; Padovani, Paolo

    1997-01-01

    We have selected quasars with X-ray colors suggestive of a low energy cut-off, from the ROSAT PSPC pointed archive. We examine the radio and optical properties of these 13 quasars. Five out of the seven quasars with good optical spectra show associated optical absorption lines, with two having high delta-v candidate systems. Two other cut-off quasars show reddening associated with the quasar. We conclude that absorption is highly likely to be the cause of the X-ray cut-offs, and that the abso...

  11. Fifty Years of Quasars From Early Observations and Ideas to Future Research

    CERN Document Server

    Marziani, Paola; Sulentic, Jack

    2012-01-01

    The 50th anniversary of the discovery of quasars in 1963 presents an interesting opportunity to ask questions about the current state of quasar research. Formatted as a series of interviews with noted researchers in the field, each of them asked to address a specific set of questions covering topics selected by the editors, this book deals with the historical development of quasar research and discusses how advances in instrumentation and computational capabilities have benefitted quasar astronomy and have changed our basic understanding of quasars. In the last part of the book the interviews address the current topic of the role of quasars in galaxy evolution. They summarise open issues in understanding active galactic nuclei and quasars and present an outlook regarding what future observational facilities both on the ground and in space might reveal. Its interview format, the fascinating topic of quasars and black holes, and the lively recollections and at times controversial views of the contributors make ...

  12. Objective-prism spectrophotometry of quasars

    International Nuclear Information System (INIS)

    Clowes, R.G.

    1980-01-01

    A procedure is derived for obtaining low-resolution spectrophotometry of quasars directly from the objective-prism plates on which they were discovered. Measurements with a PDS microdensitometer of approximately 130 quasar candidates in approximately the central 19 square degrees of the UK Schmidt prism plate UJ3682P were used in the application of the procedure. The success of the objective-prism spectrophotometry is demonstrated in a comparison with 12 slit spectra. Redshifts and equivalent widths can be determined with typical discrepancies of 1% and 40% respectively. This work on objective-prism spectrophotometry leads to a quantification of the selection effects that operate in the searches for emission-line objects on objective-prism plates. The quantification successfully explains an apparent discrepancy in the detection efficiencies of the CTIO-4m and Curtis Schmidt surveys for quasars. Spectra of quasars that were observed with the Image Photon Counting System on the Anglo-Australian Telescope are presented. The observations of quasars with broad absorption troughs indicate the ejection of matter with velocities up to approximately 22000kms -1 and with velocity dispersions up to approximately 11000kms -1 . Data on the wavelength dependences of the contrast γ and the grain response function g of the Kodak emulsion IIIaJ are presented. (author)

  13. Quasars in galaxy cluster environments

    International Nuclear Information System (INIS)

    Ellingson, E.

    1989-01-01

    The evolution of radio loud quasars is found to be strongly dependent upon their galaxy cluster environment. Previous studies have shown that bright quasars are found in rich clusters, while high luminosity quasars are found only in poorer environments. The analysis of low luminosity radio quiet quasars indicate that they are never found in rich environments, suggesting that they are a physically different class of objects. Properties of the quasar environment are investigated to determine constraints on the physical mechanisms of quasar formation and evolution. The optical cluster morphology indicates that the cluster cores have smaller radii and higher galaxy densities than are typical for low redshift clusters of similar richness. Radio morphologies may indicate that the formation of a dense intra-cluster medium is associated with the quasars' fading at these epochs. Galaxy colors appear to be normal, but there may be a tendency for clusters associated with high luminosity quasars to contain a higher fraction of gas-rich galaxies than those associated with low luminosity quasars. Multislit spectroscopic observations of galaxies associated with high luminosity quasars indicate that quasars are preferentially located in regions of low relative velocity dispersion, either in rich clusters of abnormally low dispersion, or in poor groups which are dynamically normal. This suggests that galaxy-galaxy interactions may play a role in quasar formation and sustenanace. Virialization of rich clusters and the subsequent increase in galaxy velocities may therefore be responsible for the fading of quasars in rich environments

  14. A complete quasar sample at intermediate redshift

    International Nuclear Information System (INIS)

    Cristiani, S.; La Franca, F.; Barbieri, C.; Iovino, A.

    1991-01-01

    A search for intermediate-redshift quasars has been carried out with slitless spectroscopy in the central 21.07 deg 2 of the SA 94, where the existence of a large database of objects for which slit spectroscopy was already available provided a valuable opportunity of testing the properties of our selection technique. Fifty candidates have been observed with slit spectroscopy, confirming 34 quasars and two H II galaxies. The completeness of this survey as a function of magnitude and redshift has been analysed, and an effective area of 16.9 deg 2 has been evaluated. (author)

  15. RX J1759.4+6638: An x-ray selected quasars at a redshift of 4.320

    Science.gov (United States)

    Henry, J. P.; Gioia, I. M.; Boehringer, H.; Bower, R. G.; Briel, U. G.; Hasinger, G. H.; Aragon-Salamanca, A.; Castander, F. J.; Ellis, R. S.; Huchra, J. P.

    1994-01-01

    We report the discovery of an x-ray selected Quasi-Stellar Objects (QSO) at a redshift of 4.320 +/- 0.005. This is the most distant x-ray selected object known, and it is the eighth most distant QSO known. The properties of this QSO are very similar to other QSOs at redshifts greater than 4. The x-ray discovery of this object, and that of high redshift clusters of galaxies, shows that present x-ray surveys are reaching depths competitive with other methods.

  16. Are quasars really far away

    International Nuclear Information System (INIS)

    Narlikar, J.V.

    1983-01-01

    Most astrophysicists think that quasars are distant objects. But new data, based on red-shift anomalies, and new theories embracing non-cosmological doppler effect and gravitational effects could account for the peculiarities of quasars. (U.K.)

  17. The Extremely Luminous Quasar Survey (ELQS) in SDSS and the high-z bright-end Quasar Luminosity Function

    Science.gov (United States)

    Schindler, Jan-Torge; Fan, Xiaohui; McGreer, Ian

    2018-01-01

    Studies of the most luminous quasars at high redshift directly probe the evolution of the most massive black holes in the early Universe and their connection to massive galaxy formation. Unfortunately, extremely luminous quasars at high redshift are very rare objects. Only wide area surveys have a chance to constrain their population. The Sloan Digital Sky Survey (SDSS) nd the Baryon Oscillation Spectroscopic Survey (BOSS) have so far provided the most widely adopted measurements of the type I quasar luminosity function (QLF) at z>3. However, a careful re-examination of the SDSS quasar sample revealed that the SDSS quasar selection is in fact missing a significant fraction of $z~3$ quasars at the brightest end.We have identified the purely optical color selection of SDSS, where quasars at these redshifts are strongly contaminated by late-type dwarfs, and the spectroscopic incompleteness of the SDSS footprint as the main reasons. Therefore we have designed the Extremely Luminous Quasar Survey (ELQS), based on a novel near-infrared JKW2 color cut using WISE AllWISE and 2MASS all-sky photometry, to yield high completeness for very bright (i < 18.0) quasars in the redshift range of 2.8<= z<=5.0. It effectively uses Random Forest machine-learning algorithms on SDSS and WISE photometry for quasar-star classification and photometric redshift estimation.The ELQS is spectroscopically following up ~230 new quasar candidates in an area of ~12000 deg2 in the SDSS footprint, to obtain a well-defined and complete quasar sample for an accurate measurement of the bright-end quasar luminosity function (QLF) at 2.8<= z<=5.0. So far the ELQS has identified 75 bright new quasars in this redshift range and observations of the fall sky will continue until the end of the year. At the AAS winter meeting we will present the full spectroscopic results of the survey, including a re-estimation and extension of the high-z QLF toward higher luminosities.

  18. Quasar Absorption Studies

    Science.gov (United States)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  19. Selecting Therapeutic Targets in Inflammatory Bowel Disease (STRIDE)

    DEFF Research Database (Denmark)

    Peyrin-Biroulet, L; Sandborn, W; Sands, B E

    2015-01-01

    OBJECTIVES: The Selecting Therapeutic Targets in Inflammatory Bowel Disease (STRIDE) program was initiated by the International Organization for the Study of Inflammatory Bowel Diseases (IOIBD). It examined potential treatment targets for inflammatory bowel disease (IBD) to be used for a "treat-t...... target. CONCLUSIONS: Evidence- and consensus-based recommendations for selecting the goals for treat-to-target strategies in patients with IBD are made available. Prospective studies are needed to determine how these targets will change disease course and patients' quality of life....

  20. Are quasars local

    International Nuclear Information System (INIS)

    Terrell, J.

    1974-01-01

    The problems of interpreting quasars as galaxies, at distances of billions of light-years, seem to be increasing with time and with observational knowledge. The incredibly large energy and brightness requirements, the very small size and thus high surface brightness required by their rapid fluctuations in luminosity, the recently-discovered radio-source separation speeds apparently much greater than the speed of light, their general lack of association with distant galaxies, and many other properties are all very difficult to explain on the basis of cosmological distance. The very local quasar model, involving much less massive and bright objects--perhaps similar to Type O stars--emitted at relativistic speeds by the center of our own galaxy, greatly eases these difficulties. Since such ejected objects also seem necessary to explain the similarly strange properties of radio galaxies, the emission of local quasars from some galaxies might be deduced on this basis alone. (6 figures) (U.S.)

  1. Sexual selection targets cetacean pelvic bones

    Science.gov (United States)

    Dines, J. P.; Otárola-Castillo, E.; Ralph, P.; Alas, J.; Daley, T.; Smith, A. D.; Dean, M. D.

    2014-01-01

    Male genitalia evolve rapidly, probably as a result of sexual selection. Whether this pattern extends to the internal infrastructure that influences genital movements remains unknown. Cetaceans (whales and dolphins) offer a unique opportunity to test this hypothesis: since evolving from land-dwelling ancestors, they lost external hind limbs and evolved a highly reduced pelvis which seems to serve no other function except to anchor muscles that maneuver the penis. Here we create a novel morphometric pipeline to analyze the size and shape evolution of pelvic bones from 130 individuals (29 species) in the context of inferred mating system. We present two main findings: 1) males from species with relatively intense sexual selection (inferred by relative testes size) have evolved relatively large penises and pelvic bones compared to their body size, and 2) pelvic bone shape diverges more quickly in species pairs that have diverged in inferred mating system. Neither pattern was observed in the anterior-most pair of vertebral ribs, which served as a negative control. This study provides evidence that sexual selection can affect internal anatomy that controls male genitalia. These important functions may explain why cetacean pelvic bones have not been lost through evolutionary time. PMID:25186496

  2. BINARY QUASARS AT HIGH REDSHIFT. I. 24 NEW QUASAR PAIRS AT z ∼ 3-4

    International Nuclear Information System (INIS)

    Hennawi, Joseph F.; Myers, Adam D.; Shen, Yue; Strauss, Michael A.; Djorgovski, S. G.; Glikman, Eilat; Mahabal, Ashish; Fan Xiaohui; Martin, Crystal L.; Richards, Gordon T.; Schneider, Donald P.; Shankar, Francesco

    2010-01-01

    The clustering of quasars on small scales yields fundamental constraints on models of quasar evolution and the buildup of supermassive black holes. This paper describes the first systematic survey to discover high-redshift binary quasars. Using color-selection and photometric redshift techniques, we searched 8142 deg 2 of Sloan Digital Sky Survey imaging data for binary quasar candidates, and confirmed them with follow-up spectroscopy. Our sample of 27 high-redshift binaries (24 of them new discoveries) at redshifts 2.9 perpendicular perpendicular 3.5. The completeness and efficiency of our well-defined selection algorithm are quantified using simulated photometry and we find that our sample is ∼50% complete. Our companion paper uses this knowledge to make the first measurement of the small-scale clustering (R -1 Mpc comoving) of high-redshift quasars. High-redshift binaries constitute exponentially rare coincidences of two extreme (M ∼> 10 9 M sun ) supermassive black holes. At z ∼ 4, there is about one close binary per 10 Gpc 3 , thus these could be the highest sigma peaks, the analogs of superclusters, in the early universe.

  3. FIRST-2MASS RED QUASARS: TRANSITIONAL OBJECTS EMERGING FROM THE DUST

    International Nuclear Information System (INIS)

    Glikman, Eilat; Urrutia, Tanya; Lacy, Mark; Djorgovski, S. George; Mahabal, Ashish; Myers, Adam D.; Ross, Nicholas P.; Petitjean, Patrick; Ge, Jian; Schneider, Donald P.; York, Donald G.

    2012-01-01

    We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4 GHz in the Faint Images of the Radio Sky at Twenty Centimeters survey with the near-infrared Two Micron All Sky Survey catalog and color-selecting red sources. Optical and/or near-infrared spectroscopy provide broad wavelength sampling of their spectral energy distributions that we use to determine their reddening, characterized by E(B – V). We demonstrate that the reddening in these quasars is best described by Small-Magellanic-Cloud-like dust. This sample spans a wide range in redshift and reddening (0.1 ∼< z ∼< 3, 0.1 ∼< E(B – V) ∼< 1.5), which we use to investigate the possible correlation of luminosity with reddening. At every redshift, dust-reddened quasars are intrinsically the most luminous quasars. We interpret this result in the context of merger-driven quasar/galaxy co-evolution where these reddened quasars are revealing an emergent phase during which the heavily obscured quasar is shedding its cocoon of dust prior to becoming a 'normal' blue quasar. When correcting for extinction, we find that, depending on how the parent population is defined, these red quasars make up ∼< 15%-20% of the luminous quasar population. We estimate, based on the fraction of objects in this phase, that its duration is 15%-20% as long as the unobscured, blue quasar phase.

  4. Gravitationally Lensed Quasars in Gaia: II. Discovery of 24 Lensed Quasars

    Science.gov (United States)

    Lemon, Cameron A.; Auger, Matthew W.; McMahon, Richard G.; Ostrovski, Fernanda

    2018-04-01

    We report the discovery, spectroscopic confirmation and preliminary characterisation of 24 gravitationally lensed quasars identified using Gaia observations. Candidates were selected in the Pan-STARRS footprint with quasar-like WISE colours or as photometric quasars from SDSS, requiring either multiple detections in Gaia or a single Gaia detection near a morphological galaxy. The Pan-STARRS grizY images were modelled for the most promising candidates and 60 candidate systems were followed up with the William Herschel Telescope. 13 of the lenses were discovered as Gaia multiples and 10 as single Gaia detections near galaxies. We also discover 1 lens identified through a quasar emission line in an SDSS galaxy spectrum. The lenses have median image separation 2.13″ and the source redshifts range from 1.06 to 3.36. 4 systems are quadruply-imaged and 20 are doubly-imaged. Deep CFHT data reveal an Einstein ring in one double system. We also report 12 quasar pairs, 10 of which have components at the same redshift and require further follow-up to rule out the lensing hypothesis. We compare the properties of these lenses and other known lenses recovered by our search method to a complete sample of simulated lenses to show the lenses we are missing are mainly those with small separations and higher source redshifts. The initial Gaia data release only catalogues all images of ˜ 30% of known bright lensed quasars, however the improved completeness of Gaia data release 2 will help find all bright lensed quasars on the sky.

  5. Quasar Astrophysics with the Space Interferometry Mission

    Science.gov (United States)

    Unwin, Stephen; Wehrle, Ann; Meier, David; Jones, Dayton; Piner, Glenn

    2007-01-01

    Optical astrometry of quasars and active galaxies can provide key information on the spatial distribution and variability of emission in compact nuclei. The Space Interferometry Mission (SIM PlanetQuest) will have the sensitivity to measure a significant number of quasar positions at the microarcsecond level. SIM will be very sensitive to astrometric shifts for objects as faint as V = 19. A variety of AGN phenomena are expected to be visible to SIM on these scales, including time and spectral dependence in position offsets between accretion disk and jet emission. These represent unique data on the spatial distribution and time dependence of quasar emission. It will also probe the use of quasar nuclei as fundamental astrometric references. Comparisons between the time-dependent optical photocenter position and VLBI radio images will provide further insight into the jet emission mechanism. Observations will be tailored to each specific target and science question. SIM will be able to distinguish spatially between jet and accretion disk emission; and it can observe the cores of galaxies potentially harboring binary supermassive black holes resulting from mergers.

  6. Target Selection Models with Preference Variation Between Offenders

    NARCIS (Netherlands)

    Townsley, Michael; Birks, Daniel; Ruiter, Stijn; Bernasco, Wim; White, Gentry

    2016-01-01

    Objectives: This study explores preference variation in location choice strategies of residential burglars. Applying a model of offender target selection that is grounded in assertions of the routine activity approach, rational choice perspective, crime pattern and social disorganization theories,

  7. An algorithm for preferential selection of spectroscopic targets in LEGUE

    International Nuclear Information System (INIS)

    Carlin, Jeffrey L.; Newberg, Heidi Jo; Lépine, Sébastien; Deng Licai; Chen Yuqin; Fu Xiaoting; Gao Shuang; Li Jing; Liu Chao; Beers, Timothy C.; Christlieb, Norbert; Grillmair, Carl J.; Guhathakurta, Puragra; Han Zhanwen; Hou Jinliang; Lee, Hsu-Tai; Liu Xiaowei; Pan Kaike; Sellwood, J. A.; Wang Hongchi

    2012-01-01

    We describe a general target selection algorithm that is applicable to any survey in which the number of available candidates is much larger than the number of objects to be observed. This routine aims to achieve a balance between a smoothly-varying, well-understood selection function and the desire to preferentially select certain types of targets. Some target-selection examples are shown that illustrate different possibilities of emphasis functions. Although it is generally applicable, the algorithm was developed specifically for the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) survey that will be carried out using the Chinese Guo Shou Jing Telescope. In particular, this algorithm was designed for the portion of LEGUE targeting the Galactic halo, in which we attempt to balance a variety of science goals that require stars at fainter magnitudes than can be completely sampled by LAMOST. This algorithm has been implemented for the halo portion of the LAMOST pilot survey, which began in October 2011.

  8. The luminosity function of quasars

    Science.gov (United States)

    Pei, Yichuan C.

    1995-01-01

    We propose a new evolutionary model for the optical luminosity function of quasars. Our analytical model is derived from fits to the empirical luminosity function estimated by Hartwick and Schade and Warren, Hewett, and Osmer on the basis of more than 1200 quasars over the range of redshifts 0 approximately less than z approximately less than 4.5. We find that the evolution of quasars over this entire redshift range can be well fitted by a Gaussian distribution, while the shape of the luminosity function can be well fitted by either a double power law or an exponential L(exp 1/4) law. The predicted number counts of quasars, as a function of either apparent magnitude or redshift, are fully consistent with the observed ones. Our model indicates that the evolution of quasars reaches its maximum at z approximately = 2.8 and declines at higher redshifts. An extrapolation of the evolution to z approximately greater than 4.5 implies that quasars may have started their cosmic fireworks at z(sub f) approximately = 5.2-5.5. Forthcoming surveys of quasars at these redshifts will be critical to constrain the epoch of quasar formation. All the results we derived are based on observed quasars and are therefore subject to the bias of obscuration by dust in damped Ly alpha systems. Future surveys of these absorption systems at z approximately greater than 3 will also be important if the formation epoch of quasars is to be known unambiguously.

  9. Target selection biases from recent experience transfer across effectors.

    Science.gov (United States)

    Moher, Jeff; Song, Joo-Hyun

    2016-02-01

    Target selection is often biased by an observer's recent experiences. However, not much is known about whether these selection biases influence behavior across different effectors. For example, does looking at a red object make it easier to subsequently reach towards another red object? In the current study, we asked observers to find the uniquely colored target object on each trial. Randomly intermixed pre-trial cues indicated the mode of action: either an eye movement or a visually guided reach movement to the target. In Experiment 1, we found that priming of popout, reflected in faster responses following repetition of the target color on consecutive trials, occurred regardless of whether the effector was repeated from the previous trial or not. In Experiment 2, we examined whether an inhibitory selection bias away from a feature could transfer across effectors. While priming of popout reflects both enhancement of the repeated target features and suppression of the repeated distractor features, the distractor previewing effect isolates a purely inhibitory component of target selection in which a previewed color is presented in a homogenous display and subsequently inhibited. Much like priming of popout, intertrial suppression biases in the distractor previewing effect transferred across effectors. Together, these results suggest that biases for target selection driven by recent trial history transfer across effectors. This indicates that representations in memory that bias attention towards or away from specific features are largely independent from their associated actions.

  10. X-ray spectra of PG quasars. I. The continuum from X-rays to infrared

    International Nuclear Information System (INIS)

    Elvis, M.; Green, R.F.; Bechtold, J.; Schmidt, M.; Neugebauer, G.; Kitt Peak National Observatory, Tucson, AZ; Steward Observatory, Tucson, AZ; Palomar Observatory, Pasadena, CA)

    1986-01-01

    Einstein IPC X-ray spectra for a sample of eight optically selected quasars from the Palomar Bright Quasar survey are presented. The quasars have a mean power law energy slope which in five individual cases is inconsistent with the value found in hard X-ray selection criterion rather than luminosity, redshift, or U-B color. New IUE and optical continuum spectra and infrared photometry are presented for these quasars. The data are combined into log vf(v) and log v distributions which support the decomposition of the overall quasar spectrum into a power law plus a superposed optical-UV big bump which may be due to an accretion disk. At least six of the quasars have vf(v)s which are roughly constant between their infrared and X-ray power laws, suggesting a strong link between the two regions. 104 references

  11. Nuclease Target Site Selection for Maximizing On-target Activity and Minimizing Off-target Effects in Genome Editing

    Science.gov (United States)

    Lee, Ciaran M; Cradick, Thomas J; Fine, Eli J; Bao, Gang

    2016-01-01

    The rapid advancement in targeted genome editing using engineered nucleases such as ZFNs, TALENs, and CRISPR/Cas9 systems has resulted in a suite of powerful methods that allows researchers to target any genomic locus of interest. A complementary set of design tools has been developed to aid researchers with nuclease design, target site selection, and experimental validation. Here, we review the various tools available for target selection in designing engineered nucleases, and for quantifying nuclease activity and specificity, including web-based search tools and experimental methods. We also elucidate challenges in target selection, especially in predicting off-target effects, and discuss future directions in precision genome editing and its applications. PMID:26750397

  12. Novel target configurations for selective ionization state studies in molybdenum

    International Nuclear Information System (INIS)

    Ilcisin, K.J.; Feldman, U.; Schwob, J.L.; Wouters, A.; Suckewer, S.; Princeton Univ., NJ

    1990-03-01

    Details of experiments aimed at achieving low ionization state selectivity in molybdenum are presented. Targets are excited with a 10 J CO 2 laser and the resultant VUV spectrum (300--700 Angstrom) has been studied. Combinations of focal spot size, target depth, and target geometries are compared. Simple attenuation of energy is shown not to vary ionization stage composition significantly. Experiments conducted with grazing incidence targets result only in a hot plasma. Modular targets with cooling cylinders of various radii demonstrated good selectivity of the ionization states, but with low absolute signals. Finally, results from combinations of focal spot adjustment and radiative cooling illustrate increased control over desired plasma temperature and density for spectroscopic studies of molybdenum. 7 refs., 14 figs

  13. A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey IV

    DEFF Research Database (Denmark)

    Fan, Xiaohui; Strauss, Michael A.; Richards, Gordon T.

    2005-01-01

    We present the discovery of seven quasars at z>5.7, selected from ~2000 deg^2 of multicolor imaging data of the Sloan Digital Sky Survey (SDSS). The new quasars have redshifts z from 5.79 to 6.13. Five are selected as part of a complete flux-limited sample in the SDSS Northern Galactic Cap; two...

  14. Quasars in the field of SA94. III. A colour survey

    International Nuclear Information System (INIS)

    Cristiani, S.; Barbieri, C.; La Franca, F.; Nota, A.

    1989-01-01

    A new sample of quasars has been selected in the central 10 square degrees of SA 94. The colour-colour U - B, B - V diagram has been used to identify low-redshift quasar candidates down to B = 19.8.99 extragalactic emission-line objects have been spectroscopically confirmed. The quasar surface density for QSOs with z ≤ 2.25 and other properties of this sample are derived and compared with other surveys

  15. The QUASAR facility

    Science.gov (United States)

    Gates, David

    2013-10-01

    The QUAsi-Axisymmetric Research (QUASAR) stellarator is a new facility which can solve two critical problems for fusion, disruptions and steady-state, and which provides new insights into the role of magnetic symmetry in plasma confinement. If constructed it will be the only quasi-axisymmetric stellarator in the world. The innovative principle of quasi-axisymmetry (QA) will be used in QUASAR to study how ``tokamak-like'' systems can be made: 1) Disruption-free, 2) Steady-state with low recirculating power, while preserving or improving upon features of axisymmetric tokamaks, such as 1) Stable at high pressure simultaneous with 2) High confinement (similar to tokamaks), and 3) Scalable to a compact reactor Stellarator research is critical to fusion research in order to establish the physics basis for a magnetic confinement device that can operate efficiently in steady-state, without disruptions at reactor-relevant parameters. The two large stellarator experiments - LHD in Japan and W7-X under construction in Germany are pioneering facilities capable of developing 3D physics understanding at large scale and for very long pulses. The QUASAR design is unique in being QA and optimized for confinement, stability, and moderate aspect ratio (4.5). It projects to a reactor with a major radius of ~8 m similar to advanced tokamak concepts. It is striking that (a) the EU DEMO is a pulsed (~2.5 hour) tokamak with major R ~ 9 m and (b) the ITER physics scenarios do not presume steady-state behavior. Accordingly, QUASAR fills a critical gap in the world stellarator program. This work supported by DoE Contract No. DEAC02-76CH03073.

  16. Quasars and cosmology

    International Nuclear Information System (INIS)

    Fliche, H.-H.; Souriau, J.-M.

    1978-03-01

    On the basis of colorimetric data a composite spectrum of quasars is established from the visible to the Lyman's limit. Its agreement with the spectrum of the quasar 3C273, obtained directly, confirms the homogeneity of these objects. The compatibility of the following hypotheses: negligible evolution of quasars, Friedmann type model of the universe with cosmological constant, is studied by means of two tests: a non-correlation test adopted to the observation conditions and the construction of diagrams (absolute magnitude, volume) using the K-correction deduced from the composite spectrum. This procedure happens to give relatively well-defined values of the parameters; the central values of the density parameter, the reduced curvature and the reduced cosmological constant are: Ω 0 =0.053, k 0 =0.245, lambda-zero=1.19, which correspond to a big bang model, eternally expanding, spatially finite, in which Hubble's parameter H is presently increasing. This model responds well to different cosmological tests: density of matter, diameter of radio sources, age of the universe. Its characteristics suggest various cosmogonic mechanisms, espacially mass formation by growth of empty spherical bubbles [fr

  17. A search for changing look quasars in second epoch imaging

    Science.gov (United States)

    Findlay, Joseph; Myers, Adam; McGreer, Ian

    2018-01-01

    Over nearly two decades, the Sloan Digital Sky Survey has compiled a catalog of over half a million confirmed quasars. During that period approximately ten percent of these objects have been spectroscopically observed in two or more epochs over baselines of ten or more years. This led recently to the discovery of the largest change in luminosity ever before observed in a quasar. The dimming emission was a reflection of very significant changes in continuum and broad line properties, the source had effectively transitioned from a Type I quasar to a Type II AGN. Since then several more "changing look" quasars have been discovered in multi-epoch SDSS spectroscopy. Among them are objects with rising and falling luminosities, appearing and disappearing broad lines. The origin of this behavior is still very uncertain, currently favored is the scenario in which an accreting black hole is simply starved of fuel. Other plausible scenarios include flaring due to stellar tidal disruption close to the black hole or large changes in accretion flow, which can occur during transitions between radiatively efficient and inefficient accretion regimes. Monitoring of larger numbers of changing look quasars will help to elucidate these ideas.In this poster, we report on the progress of a pilot study in which we hope to learn how to select changing look quasars in multi-epoch imaging. This will allow us to take advantage of the entire SDSS quasar catalog rather than just the ten percent of objects with multi-epoch spectroscopy. Comparing archival SDSS and more recent Legacy Survey imaging over ten-year baselines we select objects whose photometry is consistent with the large changes in luminosity expected in changing look quasars. We aim to build up a catalog of both transitioned and transitioning objects for future monitoring.

  18. First Discoveries of z > 6 Quasars with the DECam Legacy Survey and UKIRT Hemisphere Survey

    International Nuclear Information System (INIS)

    Wang, Feige; Yang, Jinyi; Wu, Xue-Bing; Yang, Qian; Li, Zefeng; Fan, Xiaohui; McGreer, Ian D.; Ding, Jiani; Green, Richard; Bian, Fuyan; Li, Jiang-Tao; Dey, Arjun; Dye, Simon; Findlay, Joseph R.; Myers, Adam D.; James, David; Jiang, Linhua; Lang, Dustin; Lawrence, Andy; Ross, Nicholas P.

    2017-01-01

    We present the first discoveries from a survey of z ≳ 6 quasars using imaging data from the DECam Legacy Survey (DECaLS) in the optical, the UKIRT Deep Infrared Sky Survey (UKIDSS) and a preliminary version of the UKIRT Hemisphere Survey (UHS) in the near-IR, and ALLWISE in the mid-IR. DECaLS will image 9000 deg 2 of sky down to z AB ∼ 23.0, and UKIDSS and UHS will map the northern sky at 0 < decl. < +60°, reaching J VEGA ∼ 19.6 (5- σ ). The combination of these data sets allows us to discover quasars at redshift z ≳ 7 and to conduct a complete census of the faint quasar population at z ≳ 6. In this paper, we report on the selection method of our search, and on the initial discoveries of two new, faint z ≳ 6 quasars and one new z = 6.63 quasar in our pilot spectroscopic observations. The two new z ∼ 6 quasars are at z = 6.07 and z = 6.17 with absolute magnitudes at rest-frame wavelength 1450 Å being M 1450 = −25.83 and M 1450 = −25.76, respectively. These discoveries suggest that we can find quasars close to or fainter than the break magnitude of the Quasar Luminosity Function (QLF) at z ≳ 6. The new z = 6.63 quasar has an absolute magnitude of M 1450 = −25.95. This demonstrates the potential of using the combined DECaLS and UKIDSS/UHS data sets to find z ≳ 7 quasars. Extrapolating from previous QLF measurements, we predict that these combined data sets will yield ∼200 z ∼ 6 quasars to z AB < 21.5, ∼1000 z ∼ 6 quasars to z AB < 23, and ∼30 quasars at z > 6.5 to J VEGA < 19.5.

  19. The quasar luminosity function at redshift 4 with the Hyper Suprime-Cam Wide Survey

    Science.gov (United States)

    Akiyama, Masayuki; He, Wanqiu; Ikeda, Hiroyuki; Niida, Mana; Nagao, Tohru; Bosch, James; Coupon, Jean; Enoki, Motohiro; Imanishi, Masatoshi; Kashikawa, Nobunari; Kawaguchi, Toshihiro; Komiyama, Yutaka; Lee, Chien-Hsiu; Matsuoka, Yoshiki; Miyazaki, Satoshi; Nishizawa, Atsushi J.; Oguri, Masamune; Ono, Yoshiaki; Onoue, Masafusa; Ouchi, Masami; Schulze, Andreas; Silverman, John D.; Tanaka, Manobu M.; Tanaka, Masayuki; Terashima, Yuichi; Toba, Yoshiki; Ueda, Yoshihiro

    2018-01-01

    We present the luminosity function of z ˜ 4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg2. From stellar objects, 1666 z ˜ 4 quasar candidates are selected via the g-dropout selection down to i = 24.0 mag. Their photometric redshifts cover the redshift range between 3.6 and 4.3, with an average of 3.9. In combination with the quasar sample from the Sloan Digital Sky Survey in the same redshift range, a quasar luminosity function covering the wide luminosity range of M1450 = -22 to -29 mag is constructed. The quasar luminosity function is well described by a double power-law model with a knee at M1450 = -25.36 ± 0.13 mag and a flat faint-end slope with a power-law index of -1.30 ± 0.05. The knee and faint-end slope show no clear evidence of redshift evolution from those seen at z ˜ 2. The flat slope implies that the UV luminosity density of the quasar population is dominated by the quasars around the knee, and does not support the steeper faint-end slope at higher redshifts reported at z > 5. If we convert the M1450 luminosity function to the hard X-ray 2-10 keV luminosity function using the relation between the UV and X-ray luminosity of quasars and its scatter, the number density of UV-selected quasars matches well with that of the X-ray-selected active galactic nuclei (AGNs) above the knee of the luminosity function. Below the knee, the UV-selected quasars show a deficiency compared to the hard X-ray luminosity function. The deficiency can be explained by the lack of obscured AGNs among the UV-selected quasars.

  20. DISCOVERING THE MISSING 2.2 < z < 3 QUASARS BY COMBINING OPTICAL VARIABILITY AND OPTICAL/NEAR-INFRARED COLORS

    International Nuclear Information System (INIS)

    Wu Xuebing; Wang Ran; Bian Fuyan; Jiang Linhua; Fan Xiaohui; Schmidt, Kasper B.

    2011-01-01

    The identification of quasars in the redshift range 2.2 < z < 3 is known to be very inefficient because the optical colors of such quasars are indistinguishable from those of stars. Recent studies have proposed using optical variability or near-infrared (near-IR) colors to improve the identification of the missing quasars in this redshift range. Here we present a case study combining both methods. We select a sample of 70 quasar candidates from variables in Sloan Digital Sky Survey (SDSS) Stripe 82, which are non-ultraviolet excess sources and have UKIDSS near-IR public data. They are clearly separated into two parts on the Y - K/g - z color-color diagram, and 59 of them meet or lie close to a newly proposed Y - K/g - z selection criterion for z < 4 quasars. Of these 59 sources, 44 were previously identified as quasars in SDSS DR7, and 35 of them are quasars at 2.2 < z < 3. We present spectroscopic observations of 14 of 15 remaining quasar candidates using the Bok 2.3 m telescope and the MMT 6.5 m telescope, and successfully identify all of them as new quasars at z = 2.36-2.88. We also apply this method to a sample of 643 variable quasar candidates with SDSS-UKIDSS nine-band photometric data selected from 1875 new quasar candidates in SDSS Stripe 82 given by Butler and Bloom based on the time-series selections, and find that 188 of them are probably new quasars with photometric redshifts at 2.2 < z < 3. Our results indicate that the combination of optical variability and optical/near-IR colors is probably the most efficient way to find 2.2 < z < 3 quasars and is very helpful for constructing a complete quasar sample. We discuss its implications for ongoing and upcoming large optical and near-IR sky surveys.

  1. In-silico Leishmania Target Selectivity of Antiparasitic Terpenoids

    Directory of Open Access Journals (Sweden)

    Ifedayo Victor Ogungbe

    2013-07-01

    Full Text Available Neglected Tropical Diseases (NTDs, like leishmaniasis, are major causes of mortality in resource-limited countries. The mortality associated with these diseases is largely due to fragile healthcare systems, lack of access to medicines, and resistance by the parasites to the few available drugs. Many antiparasitic plant-derived isoprenoids have been reported, and many of them have good in vitro activity against various forms of Leishmania spp. In this work, potential Leishmania biochemical targets of antiparasitic isoprenoids were studied in silico. Antiparasitic monoterpenoids selectively docked to L. infantum nicotinamidase, L. major uridine diphosphate-glucose pyrophosphorylase and methionyl t-RNA synthetase. The two protein targets selectively targeted by germacranolide sesquiterpenoids were L. major methionyl t-RNA synthetase and dihydroorotate dehydrogenase. Diterpenoids generally favored docking to L. mexicana glycerol-3-phosphate dehydrogenase. Limonoids also showed some selectivity for L. mexicana glycerol-3-phosphate dehydrogenase and L. major dihydroorotate dehydrogenase while withanolides docked more selectively with L. major uridine diphosphate-glucose pyrophosphorylase. The selectivity of the different classes of antiparasitic compounds for the protein targets considered in this work can be explored in fragment- and/or structure-based drug design towards the development of leads for new antileishmanial drugs.

  2. Improved targeted immunization strategies based on two rounds of selection

    Science.gov (United States)

    Xia, Ling-Ling; Song, Yu-Rong; Li, Chan-Chan; Jiang, Guo-Ping

    2018-04-01

    In the case of high degree targeted immunization where the number of vaccine is limited, when more than one node associated with the same degree meets the requirement of high degree centrality, how can we choose a certain number of nodes from those nodes, so that the number of immunized nodes will not exceed the limit? In this paper, we introduce a new idea derived from the selection process of second-round exam to solve this problem and then propose three improved targeted immunization strategies. In these proposed strategies, the immunized nodes are selected through two rounds of selection, where we increase the quotas of first-round selection according the evaluation criterion of degree centrality and then consider another characteristic parameter of node, such as node's clustering coefficient, betweenness and closeness, to help choose targeted nodes in the second-round selection. To validate the effectiveness of the proposed strategies, we compare them with the degree immunizations including the high degree targeted and the high degree adaptive immunizations using two metrics: the size of the largest connected component of immunized network and the number of infected nodes. Simulation results demonstrate that the proposed strategies based on two rounds of sorting are effective for heterogeneous networks and their immunization effects are better than that of the degree immunizations.

  3. Feature Extraction and Selection Strategies for Automated Target Recognition

    Science.gov (United States)

    Greene, W. Nicholas; Zhang, Yuhan; Lu, Thomas T.; Chao, Tien-Hsin

    2010-01-01

    Several feature extraction and selection methods for an existing automatic target recognition (ATR) system using JPLs Grayscale Optical Correlator (GOC) and Optimal Trade-Off Maximum Average Correlation Height (OT-MACH) filter were tested using MATLAB. The ATR system is composed of three stages: a cursory region of-interest (ROI) search using the GOC and OT-MACH filter, a feature extraction and selection stage, and a final classification stage. Feature extraction and selection concerns transforming potential target data into more useful forms as well as selecting important subsets of that data which may aide in detection and classification. The strategies tested were built around two popular extraction methods: Principal Component Analysis (PCA) and Independent Component Analysis (ICA). Performance was measured based on the classification accuracy and free-response receiver operating characteristic (FROC) output of a support vector machine(SVM) and a neural net (NN) classifier.

  4. Outshining the quasars at reionization

    DEFF Research Database (Denmark)

    Watson, D.; Reeves, J.N.; Hjorth, J.

    2006-01-01

    Gamma Rays: Bursts, Galaxies: Intergalactic Medium, Galaxies: Quasars: Absorption Lines, X-Rays: Galaxies, X-Rays: General Udgivelsesdato: 19 January......Gamma Rays: Bursts, Galaxies: Intergalactic Medium, Galaxies: Quasars: Absorption Lines, X-Rays: Galaxies, X-Rays: General Udgivelsesdato: 19 January...

  5. A main sequence for quasars

    Science.gov (United States)

    Marziani, Paola; Dultzin, Deborah; Sulentic, Jack W.; Del Olmo, Ascensión; Negrete, C. A.; Martínez-Aldama, Mary L.; D'Onofrio, Mauro; Bon, Edi; Bon, Natasa; Stirpe, Giovanna M.

    2018-03-01

    The last 25 years saw a major step forward in the analysis of optical and UV spectroscopic data of large quasar samples. Multivariate statistical approaches have led to the definition of systematic trends in observational properties that are the basis of physical and dynamical modeling of quasar structure. We discuss the empirical correlates of the so-called “main sequence” associated with the quasar Eigenvector 1, its governing physical parameters and several implications on our view of the quasar structure, as well as some luminosity effects associated with the virialized component of the line emitting regions. We also briefly discuss quasars in a segment of the main sequence that includes the strongest FeII emitters. These sources show a small dispersion around a well-defined Eddington ratio value, a property which makes them potential Eddington standard candles.

  6. A Main Sequence for Quasars

    Directory of Open Access Journals (Sweden)

    Paola Marziani

    2018-03-01

    Full Text Available The last 25 years saw a major step forward in the analysis of optical and UV spectroscopic data of large quasar samples. Multivariate statistical approaches have led to the definition of systematic trends in observational properties that are the basis of physical and dynamical modeling of quasar structure. We discuss the empirical correlates of the so-called “main sequence” associated with the quasar Eigenvector 1, its governing physical parameters and several implications on our view of the quasar structure, as well as some luminosity effects associated with the virialized component of the line emitting regions. We also briefly discuss quasars in a segment of the main sequence that includes the strongest FeII emitters. These sources show a small dispersion around a well-defined Eddington ratio value, a property which makes them potential Eddington standard candles.

  7. Classification and Target Group Selection Based Upon Frequent Patterns

    NARCIS (Netherlands)

    W.H.L.M. Pijls (Wim); R. Potharst (Rob)

    2000-01-01

    textabstractIn this technical report , two new algorithms based upon frequent patterns are proposed. One algorithm is a classification method. The other one is an algorithm for target group selection. In both algorithms, first of all, the collection of frequent patterns in the training set is

  8. Burglar Target Selection: A Cross-National Comparison

    NARCIS (Netherlands)

    Townsley, M.; Birks, D.; Bernasco, W.; Johnson, S.D.; Ruiter, S.; White, G.

    2015-01-01

    Objectives: This study builds on research undertaken by Bernasco and Nieuwbeerta and explores the generalizability of a theoretically derived offender target selection model in three cross-national study regions. Methods: Taking a discrete spatial choice approach, we estimate the impact of both

  9. Burglar Target Selection : A Cross-national Comparison

    NARCIS (Netherlands)

    Townsley, Michael; Birks, Daniel; Bernasco, Wim; Ruiter, Stijn; Johnson, Shane D.; White, Gentry; Baum, Scott

    Objectives: This study builds on research undertaken by Bernasco and Nieuwbeerta and explores the generalizability of a theoretically derived offender target selection model in three cross-national study regions. Methods: Taking a discrete spatial choice approach, we estimate the impact of both

  10. Neural Networks for Target Selection in Direct Marketing

    NARCIS (Netherlands)

    R. Potharst (Rob); U. Kaymak (Uzay); W.H.L.M. Pijls (Wim)

    2001-01-01

    textabstractPartly due to a growing interest in direct marketing, it has become an important application field for data mining. Many techniques have been applied to select the targets in commercial applications, such as statistical regression, regression trees, neural computing, fuzzy clustering

  11. Targeted Diazotransfer Reagents Enable Selective Modification of Proteins with Azides.

    Science.gov (United States)

    Lohse, Jonas; Swier, Lotteke J Y M; Oudshoorn, Ruben C; Médard, Guillaume; Kuster, Bernhard; Slotboom, Dirk-Jan; Witte, Martin D

    2017-04-19

    In chemical biology, azides are used to chemically manipulate target structures in a bioorthogonal manner for a plethora of applications ranging from target identification to the synthesis of homogeneously modified protein conjugates. While a variety of methods have been established to introduce the azido group into recombinant proteins, a method that directly converts specific amino groups in endogenous proteins is lacking. Here, we report the first biotin-tethered diazotransfer reagent DtBio and demonstrate that it selectively modifies the model proteins streptavidin and avidin and the membrane protein BioY on cell surface. The reagent converts amines in the proximity of the binding pocket to azides and leaves the remaining amino groups in streptavidin untouched. Reagents of this novel class will find use in target identification as well as the selective functionalization and bioorthogonal protection of proteins.

  12. Studies of Quasar Outflows

    Science.gov (United States)

    Arav, Nahum

    2002-01-01

    The main aim of this research program is to determine the ionization equilibrium and abundances in quasar outflows. Especially in the broad absorption line QSO PG 0946+301. We find that the outflow's metalicity is consistent with being solar, while the abundance ratio of phosphorus to other metals is at least ten times solar. These findings are based on diagnostics that are not sensitive to saturation and partial covering effects in the BALs (Broad Adsorption Lines), which considerably weakened previous claims for enhanced metalicity. Ample evidence for these effects is seen in the spectrum.

  13. NuSTAR observations of heavily obscured quasars at z ~ 0.5

    DEFF Research Database (Denmark)

    Lansbury, G. B.; Alexander, D. M.; Del Moro, A.

    2014-01-01

    We present NuSTAR hard X-ray observations of three Type 2 quasars at z ≈ 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O III] luminosity ratio and multiwavelength...

  14. Observing broad-absorption line quasars with Spectrum-Rontgen-Gamma

    DEFF Research Database (Denmark)

    Singh, K.P.; Schnopper, H.W.; Westergaard, Niels Jørgen Stenfeldt

    1998-01-01

    Broad-absorption line quasars are found to have extremely weak soft X-ray emission when compared with other optically selected quasars. In the only example of PHL 5200 for which a detailed X-ray spectrum has been obtained with ASCA, strong absorption in the source appears to be responsible...

  15. Narrow CIV lambda 1549A Absorption Lines in Moderate-Redshift Quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2002-01-01

    A large, high-quality spectral data base of well-selected, moderate-redshift radio-loud and radio-quiet quasars is used to characterize the incidence of narrow associated CIV lambda 1549 absorption, and how this may depend on some quasar properties, including radio-type. Preliminary results...

  16. Target Selection for the SDSS-IV APOGEE-2 Survey

    Energy Technology Data Exchange (ETDEWEB)

    Zasowski, G. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Cohen, R. E.; Carlberg, J. K.; Fleming, Scott W. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Chojnowski, S. D.; Holtzman, J. [Department of Astronomy, New Mexico State University, Las Cruces, NM 88001 (United States); Santana, F. [Departamento de Astronomía, Universidad de Chile, Santiago (Chile); Oelkers, R. J.; Bird, J. C. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Andrews, B. [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Beaton, R. L. [The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States); Bender, C.; Cunha, K. [Steward Observatory, The University of Arizona, Tucson, AZ 85719 (United States); Bovy, J. [Department of Astronomy and Astrophysics and Dunlap Institute for Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Covey, K. [Department of Physics and Astronomy, Western Washington University, Bellingham, WA 98225 (United States); Dell’Agli, F.; García-Hernández, D. A. [Departamento de Astrofísica, Universidad de La Laguna, and Instituto de Astrofísica de Canarias, La Laguna, Tenerife (Spain); Frinchaboy, P. M. [Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129 (United States); Harding, P. [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Johnson, J. A., E-mail: gail.zasowski@gmail.com [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States); and others

    2017-11-01

    APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing ∼3 × 10{sup 5} stars across the entire sky. It is the successor to APOGEE and is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding on APOGEE’s goals of addressing critical questions of stellar astrophysics, stellar populations, and Galactic chemodynamical evolution using (1) an enhanced set of target types and (2) a second spectrograph at Las Campanas Observatory in Chile. APOGEE-2 is targeting red giant branch and red clump stars, RR Lyrae, low-mass dwarf stars, young stellar objects, and numerous other Milky Way and Local Group sources across the entire sky from both hemispheres. In this paper, we describe the APOGEE-2 observational design, target selection catalogs and algorithms, and the targeting-related documentation included in the SDSS data releases.

  17. Target Selection for the SDSS-IV APOGEE-2 Survey

    International Nuclear Information System (INIS)

    Zasowski, G.; Cohen, R. E.; Carlberg, J. K.; Fleming, Scott W.; Chojnowski, S. D.; Holtzman, J.; Santana, F.; Oelkers, R. J.; Bird, J. C.; Andrews, B.; Beaton, R. L.; Bender, C.; Cunha, K.; Bovy, J.; Covey, K.; Dell’Agli, F.; García-Hernández, D. A.; Frinchaboy, P. M.; Harding, P.; Johnson, J. A.

    2017-01-01

    APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing ∼3 × 10 5 stars across the entire sky. It is the successor to APOGEE and is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding on APOGEE’s goals of addressing critical questions of stellar astrophysics, stellar populations, and Galactic chemodynamical evolution using (1) an enhanced set of target types and (2) a second spectrograph at Las Campanas Observatory in Chile. APOGEE-2 is targeting red giant branch and red clump stars, RR Lyrae, low-mass dwarf stars, young stellar objects, and numerous other Milky Way and Local Group sources across the entire sky from both hemispheres. In this paper, we describe the APOGEE-2 observational design, target selection catalogs and algorithms, and the targeting-related documentation included in the SDSS data releases.

  18. DOUBLE QUASARS: PROBES OF BLACK HOLE SCALING RELATIONSHIPS AND MERGER SCENARIOS

    International Nuclear Information System (INIS)

    Foreman, G.; Volonteri, M.; Dotti, M.

    2009-01-01

    We analyze the available sample of double quasars, and investigate their physical properties. Our sample comprises 85 pairs, selected from the Sloan Digital Sky Survey (SDSS). We derive physical parameters for the engine and the host, and model the dynamical evolution of the pair. First, we compare different scaling relationships between massive black holes and their hosts (bulge mass, velocity dispersion, and their possible redshift dependences), and discuss their consistency. We then compute dynamical friction timescales for the double quasar systems to investigate their frequency and their agreement with the m erger drivenscenario for quasar triggering. In optical surveys, such as the SDSS, N double,qso /N qso ∼ 0.1%. Comparing typical merging timescales to expected quasar lifetimes, the fraction of double quasars should be roughly a factor of 10 larger than observed. Additionally, we find that, depending on the correlations between black holes and their hosts, the occurrence of double quasars could be redshift dependent. Comparison of our models to the SDSS quasar catalog suggests that double quasars should be more common at high redshift. We compare the typical separations at which double quasars are observed to the predictions of merger simulations. We find that the distribution of physical separations peaks at ∼30 kpc, with a tail at larger separations (∼100-200 kpc). The peak of the distribution is roughly consistent with the first episode of quasar activity found in equal mass mergers simulations. The tail of the quasar pairs distribution at large separations is instead inconsistent with any quasar activity predicted by published simulations. These large separation pairs are instead consistent with unequal mass mergers where gas is dynamically perturbed during the first pericentric passage, but the gas reaches the black hole only at the next apocenter, where the pair is observed.

  19. THE SLOAN DIGITAL SKY SURVEY QUASAR LENS SEARCH. V. FINAL CATALOG FROM THE SEVENTH DATA RELEASE

    International Nuclear Information System (INIS)

    Inada, Naohisa; Oguri, Masamune; Kayo, Issha; Fukugita, Masataka; Shin, Min-Su; Strauss, Michael A.; Bahcall, Neta A.; Morokuma, Tomoki; Rusu, Cristian E.; Kochanek, Christopher S.; Richards, Gordon T.; Schneider, Donald P.; York, Donald G.; Frieman, Joshua A.; Hall, Patrick B.; White, Richard L.

    2012-01-01

    We present the final statistical sample of lensed quasars from the Sloan Digital Sky Survey (SDSS) Quasar Lens Search (SQLS). The well-defined statistical lens sample consists of 26 lensed quasars brighter than i = 19.1 and in the redshift range of 0.6 < z < 2.2 selected from 50,826 spectroscopically confirmed quasars in the SDSS Data Release 7 (DR7), where we restrict the image separation range to 1'' < θ < 20'' and the i-band magnitude differences in two images to be smaller than 1.25 mag. The SDSS DR7 quasar catalog also contains 36 additional lenses identified with various techniques. In addition to these lensed quasars, we have identified 81 pairs of quasars from follow-up spectroscopy, 26 of which are physically associated binary quasars. The statistical lens sample covers a wide range of image separations, redshifts, and magnitudes, and therefore is suitable for systematic studies of cosmological parameters and surveys of the structure and evolution of galaxies and quasars.

  20. Integrative analysis to select cancer candidate biomarkers to targeted validation

    Science.gov (United States)

    Heberle, Henry; Domingues, Romênia R.; Granato, Daniela C.; Yokoo, Sami; Canevarolo, Rafael R.; Winck, Flavia V.; Ribeiro, Ana Carolina P.; Brandão, Thaís Bianca; Filgueiras, Paulo R.; Cruz, Karen S. P.; Barbuto, José Alexandre; Poppi, Ronei J.; Minghim, Rosane; Telles, Guilherme P.; Fonseca, Felipe Paiva; Fox, Jay W.; Santos-Silva, Alan R.; Coletta, Ricardo D.; Sherman, Nicholas E.; Paes Leme, Adriana F.

    2015-01-01

    Targeted proteomics has flourished as the method of choice for prospecting for and validating potential candidate biomarkers in many diseases. However, challenges still remain due to the lack of standardized routines that can prioritize a limited number of proteins to be further validated in human samples. To help researchers identify candidate biomarkers that best characterize their samples under study, a well-designed integrative analysis pipeline, comprising MS-based discovery, feature selection methods, clustering techniques, bioinformatic analyses and targeted approaches was performed using discovery-based proteomic data from the secretomes of three classes of human cell lines (carcinoma, melanoma and non-cancerous). Three feature selection algorithms, namely, Beta-binomial, Nearest Shrunken Centroids (NSC), and Support Vector Machine-Recursive Features Elimination (SVM-RFE), indicated a panel of 137 candidate biomarkers for carcinoma and 271 for melanoma, which were differentially abundant between the tumor classes. We further tested the strength of the pipeline in selecting candidate biomarkers by immunoblotting, human tissue microarrays, label-free targeted MS and functional experiments. In conclusion, the proposed integrative analysis was able to pre-qualify and prioritize candidate biomarkers from discovery-based proteomics to targeted MS. PMID:26540631

  1. Selective tumor cell targeting by the disaccharide moiety of bleomycin.

    Science.gov (United States)

    Yu, Zhiqiang; Schmaltz, Ryan M; Bozeman, Trevor C; Paul, Rakesh; Rishel, Michael J; Tsosie, Krystal S; Hecht, Sidney M

    2013-02-27

    In a recent study, the well-documented tumor targeting properties of the antitumor agent bleomycin (BLM) were studied in cell culture using microbubbles that had been derivatized with multiple copies of BLM. It was shown that BLM selectively targeted MCF-7 human breast carcinoma cells but not the "normal" breast cell line MCF-10A. Furthermore, it was found that the BLM analogue deglycobleomycin, which lacks the disaccharide moiety of BLM, did not target either cell line, indicating that the BLM disaccharide moiety is necessary for tumor selectivity. Not resolved in the earlier study were the issues of whether the BLM disaccharide moiety alone is sufficient for tumor cell targeting and the possible cellular uptake of the disaccharide. In the present study, we conjugated BLM, deglycoBLM, and BLM disaccharide to the cyanine dye Cy5**. It was found that the BLM and BLM disaccharide conjugates, but not the deglycoBLM conjugate, bound selectively to MCF-7 cells and were internalized. The same was also true for the prostate cancer cell line DU-145 (but not for normal PZ-HPV-7 prostate cells) and for the pancreatic cancer cell line BxPC-3 (but not for normal SVR A221a pancreas cells). The targeting efficiency of the disaccharide was only slightly less than that of BLM in MCF-7 and DU-145 cells and comparable to that of BLM in BxPC-3 cells. These results establish that the BLM disaccharide is both necessary and sufficient for tumor cell targeting, a finding with obvious implications for the design of novel tumor imaging and therapeutic agents.

  2. Target Selection for the SDSS-III MARVELS Survey

    Science.gov (United States)

    Paegert, Martin; Stassun, Keivan G.; De Lee, Nathan; Pepper, Joshua; Fleming, Scott W.; Sivarani, Thirupathi; Mahadevan, Suvrath; Mack, Claude E., III; Dhital, Saurav; Hebb, Leslie; Ge, Jian

    2015-06-01

    We present the target selection process for the Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which is part of the Sloan Digital Sky Survey (SDSS) III. MARVELS is a medium-resolution (R ∼ 11,000) multi-fiber spectrograph capable of obtaining radial velocities for 60 objects at a time in order to find brown dwarfs and giant planets. The survey was configured to target dwarf stars with effective temperatures approximately between 4500 and 6250 K. For the first 2 years MARVELS relied on low-resolution spectroscopic pre-observations to estimate the effective temperature and log (g) for candidate stars and then selected suitable dwarf stars from this pool. Ultimately, the pre-observation spectra proved ineffective at filtering out giant stars; many giants were incorrectly classified as dwarfs, resulting in a giant contamination rate of ∼30% for the first phase of the MARVELS survey. Thereafter, the survey instead applied a reduced proper motion cut to eliminate giants and used the Infrared Flux Method to estimate effective temperatures, using only extant photmetric and proper-motion catalog information. The target selection method introduced here may be useful for other surveys that need to rely on extant catalog data for selection of specific stellar populations.

  3. Serendipitous discovery of quadruply imaged quasars: two diamonds

    Science.gov (United States)

    Lucey, John R.; Schechter, Paul L.; Smith, Russell J.; Anguita, T.

    2018-05-01

    Gravitationally lensed quasars are powerful and versatile astrophysical tools, but they are challengingly rare. In particular, only ˜25 well-characterized quadruple systems are known to date. To refine the target catalogue for the forthcoming Taipan Galaxy Survey, the images of a large number of sources are being visually inspected in order to identify objects that are confused by a foreground star or galaxies that have a distinct multicomponent structure. An unexpected by-product of this work has been the serendipitous discovery of about a dozen galaxies that appear to be lensing quasars, i.e. pairs or quartets of foreground stellar objects in close proximity to the target source. Here, we report two diamond-shaped systems. Follow-up spectroscopy with the IMACS instrument on the 6.5m Magellan Baade telescope confirms one of these as a z = 1.975 quasar quadruply lensed by a double galaxy at z = 0.293. Photometry from publicly available survey images supports the conclusion that the other system is a highly sheared quadruply imaged quasar. In starting with objects thought to be galaxies, our lens finding technique complements the conventional approach of first identifying sources with quasar-like colours and subsequently finding evidence of lensing.

  4. Signatures of DNA target selectivity by ETS transcription factors.

    Science.gov (United States)

    Poon, Gregory M K; Kim, Hye Mi

    2017-05-27

    The ETS family of transcription factors is a functionally heterogeneous group of gene regulators that share a structurally conserved, eponymous DNA-binding domain. DNA target specificity derives from combinatorial interactions with other proteins as well as intrinsic heterogeneity among ETS domains. Emerging evidence suggests molecular hydration as a fundamental feature that defines the intrinsic heterogeneity in DNA target selection and susceptibility to epigenetic DNA modification. This perspective invokes novel hypotheses in the regulation of ETS proteins in physiologic osmotic stress, their pioneering potential in heterochromatin, and the effects of passive and pharmacologic DNA demethylation on ETS regulation.

  5. Luminosity function of high redshift quasars

    International Nuclear Information System (INIS)

    Vaucher, B.G.

    1982-01-01

    Data from ten different emission-line surveys are included in a study of the luminosity function of high redshift quasars. Five of the surveys are analyzed through microdensitometric techniques and the data for new quasars are given. The uncertainties in magnitudes, redshifts, and line equivalent widths are assessed and found to be +-0.3 mag. +-0.04 in z and approx. 30%, respectively. Criteria for selecting the redshift range 1.8 less than or equal to z - 1 Mpc - 1 for each of two cosmologies (q 0 = 1 and q 0 = 0). For either cosmology, the function exhibits a steep increase with magnitude at high luminosities and a gentler increase at intermediate luminosities. Data from the new surveys indicate a possible turnover at the faint end of the distribution. Total volume densities of quasars are computed for each of three extrapolations of the trend of the data to low luminosities. These densities are compared to those of active galaxies and field galaxies

  6. Nanostructured materials for selective recognition and targeted drug delivery

    International Nuclear Information System (INIS)

    Kotrotsiou, O; Kotti, K; Dini, E; Kammona, O; Kiparissides, C

    2005-01-01

    Selective recognition requires the introduction of a molecular memory into a polymer matrix in order to make it capable of rebinding an analyte with a very high specificity. In addition, targeted drug delivery requires drug-loaded vesicles which preferentially localize to the sites of injury and avoid uptake into uninvolved tissues. The rapid evolution of nanotechnology is aiming to fulfill the goal of selective recognition and optimal drug delivery through the development of molecularly imprinted polymeric (MIP) nanoparticles, tailor-made for a diverse range of analytes (e.g., pharmaceuticals, pesticides, amino acids, etc.) and of nanostructured targeted drug carriers (e.g., liposomes and micelles) with increased circulation lifetimes. In the present study, PLGA microparticles containing multilamellar vesicles (MLVs), and MIP nanoparticles were synthesized to be employed as drug carriers and synthetic receptors respectively

  7. The Sloan Digital Sky Survey Quasar Catalog: Fourteenth data release

    Science.gov (United States)

    Pâris, Isabelle; Petitjean, Patrick; Aubourg, Éric; Myers, Adam D.; Streblyanska, Alina; Lyke, Brad W.; Anderson, Scott F.; Armengaud, Éric; Bautista, Julian; Blanton, Michael R.; Blomqvist, Michael; Brinkmann, Jonathan; Brownstein, Joel R.; Brandt, William Nielsen; Burtin, Étienne; Dawson, Kyle; de la Torre, Sylvain; Georgakakis, Antonis; Gil-Marín, Héctor; Green, Paul J.; Hall, Patrick B.; Kneib, Jean-Paul; LaMassa, Stephanie M.; Le Goff, Jean-Marc; MacLeod, Chelsea; Mariappan, Vivek; McGreer, Ian D.; Merloni, Andrea; Noterdaeme, Pasquier; Palanque-Delabrouille, Nathalie; Percival, Will J.; Ross, Ashley J.; Rossi, Graziano; Schneider, Donald P.; Seo, Hee-Jong; Tojeiro, Rita; Weaver, Benjamin A.; Weijmans, Anne-Marie; Yèche, Christophe; Zarrouk, Pauline; Zhao, Gong-Bo

    2018-05-01

    We present the data release 14 Quasar catalog (DR14Q) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV). This catalog includes all SDSS-IV/eBOSS objects that were spectroscopically targeted as quasar candidates and that are confirmed as quasars via a new automated procedure combined with a partial visual inspection of spectra, have luminosities Mi [z = 2] < -20.5 (in a Λ CDM cosmology with H0 = 70 km s-1 Mpc-1, Ω M =0.3, and Ω Λ = 0.7), and either display at least one emission line with a full width at half maximum larger than 500 km s-1 or, if not, have interesting/complex absorption features. The catalog also includes previously spectroscopically-confirmed quasars from SDSS-I, II, and III. The catalog contains 526 356 quasars (144 046 are new discoveries since the beginning of SDSS-IV) detected over 9376 deg2 (2044 deg2 having new spectroscopic data available) with robust identification and redshift measured by a combination of principal component eigenspectra. The catalog is estimated to have about 0.5% contamination. Redshifts are provided for the Mg II emission line. The catalog identifies 21 877 broad absorption line quasars and lists their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra, covering the wavelength region 3610-10 140 Å at a spectral resolution in the range 1300 < R < 2500, can be retrieved from the SDSS Science Archiver Server. http://www.sdss.org/dr14/algorithms/qso_catalog

  8. A Hubble Diagram for Quasars

    Directory of Open Access Journals (Sweden)

    Susanna Bisogni

    2018-01-01

    Full Text Available The cosmological model is at present not tested between the redshift of the farthest observed supernovae (z ~ 1.4 and that of the Cosmic Microwave Background (z ~ 1,100. Here we introduce a new method to measure the cosmological parameters: we show that quasars can be used as “standard candles” by employing the non-linear relation between their intrinsic UV and X-ray emission as an absolute distance indicator. We built a sample of ~1,900 quasars with available UV and X-ray observations, and produced a Hubble Diagram up to z ~ 5. The analysis of the quasar Hubble Diagram, when used in combination with supernovae, provides robust constraints on the matter and energy content in the cosmos. The application of this method to forthcoming, larger quasar samples, will also provide tight constraints on the dark energy equation of state and its possible evolution with time.

  9. Probing black hole accretion in quasar pairs at high redshift

    Science.gov (United States)

    Vignali, C.; Piconcelli, E.; Perna, M.; Hennawi, J.; Gilli, R.; Comastri, A.; Zamorani, G.; Dotti, M.; Mathur, S.

    2018-06-01

    Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here, we present the X-ray properties of two systems of dual quasars at z = 3.0-3.3 selected from the SDSS DR6 at separations of 6-8 arcsec (43-65 kpc) and observed by Chandra for ≈65 ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z = 5 (separation of 21 arcsec, 136 kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both quasar pairs at z ≈ 3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z ≈ 3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3 per cent probability that it is by chance.

  10. Probing black hole accretion in quasar pairs at high redshift

    Science.gov (United States)

    Vignali, C.; Piconcelli, E.; Perna, M.; Hennawi, J.; Gilli, R.; Comastri, A.; Zamorani, G.; Dotti, M.; Mathur, S.

    2018-03-01

    Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here we present the X-ray properties of two systems of dual quasars at z=3.0-3.3 selected from the SDSS DR6 at separations of 6-8 arcsec (43-65 kpc) and observed by Chandra for ≈65 ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z=5 (separation of 21″, 136 kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both quasar pairs at z ≈ 3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z ≈ 3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3% probability that it is by chance.

  11. A very bright (i = 16.44) quasar in the 'redshift desert' discovered by the Guoshoujing Telescope (LAMOST)

    International Nuclear Information System (INIS)

    Wu Xuebing; Chen Zhaoyu; Jia Zhendong; Zuo Wenwen; Zhao Yongheng; Luo Ali; Bai Zhongrui; Chen Jianjun; Zhang Haotong; Yan Hongliang; Ren Juanjuan; Sun Shiwei; Wu Hong; Zhang Yong; Li Yeping; Lu Qishuai; Wang You; Ni Jijun; Wang Hai; Kong Xu

    2010-01-01

    The redshift range from 2.2 to 3 is known as the 'redshift desert' of quasars because quasars with redshifts in this range have similar optical colors as normal stars and are thus difficult to find in optical sky surveys. A quasar candidate, SDSS J085543.40-001517.7, which was selected by a recently proposed criterion involving near-IR Y - K and optical g - z colors, was identified spectroscopically as a new quasar with a redshift of 2.427 by the Guoshoujing Telescope (LAMOST) commissioning observation in 2009 December and confirmed by the observation made with the NAOC/Xinglong 2.16 m telescope in 2010 March. This quasar was not identified in the SDSS spectroscopic survey. Comparing with other SDSS quasars, we found that this new quasar, with an i magnitude of 16.44, is apparently the brightest one in the redshift range from 2.3 to 2.7. From its spectral properties, we derived its central black hole mass to be (1.4 ∼ 3.9) x 10 10 M o-dot and its bolometric luminosity to be 3.7 x 10 48 erg s -1 , which indicates that this new quasar is intrinsically very bright and belongs to the class of the most luminous quasars in the universe. Our identification supports the notion that quasars in the redshift desert can be found by the quasar selection criterion involving the near-IR colors. More missing quasars are expected to be uncovered by future LAMOST spectroscopic surveys, which is important to the study of the cosmological evolution of quasars at redshifts higher than 2.2. (research papers)

  12. Dynamic interactions between visual working memory and saccade target selection

    Science.gov (United States)

    Schneegans, Sebastian; Spencer, John P.; Schöner, Gregor; Hwang, Seongmin; Hollingworth, Andrew

    2014-01-01

    Recent psychophysical experiments have shown that working memory for visual surface features interacts with saccadic motor planning, even in tasks where the saccade target is unambiguously specified by spatial cues. Specifically, a match between a memorized color and the color of either the designated target or a distractor stimulus influences saccade target selection, saccade amplitudes, and latencies in a systematic fashion. To elucidate these effects, we present a dynamic neural field model in combination with new experimental data. The model captures the neural processes underlying visual perception, working memory, and saccade planning relevant to the psychophysical experiment. It consists of a low-level visual sensory representation that interacts with two separate pathways: a spatial pathway implementing spatial attention and saccade generation, and a surface feature pathway implementing color working memory and feature attention. Due to bidirectional coupling between visual working memory and feature attention in the model, the working memory content can indirectly exert an effect on perceptual processing in the low-level sensory representation. This in turn biases saccadic movement planning in the spatial pathway, allowing the model to quantitatively reproduce the observed interaction effects. The continuous coupling between representations in the model also implies that modulation should be bidirectional, and model simulations provide specific predictions for complementary effects of saccade target selection on visual working memory. These predictions were empirically confirmed in a new experiment: Memory for a sample color was biased toward the color of a task-irrelevant saccade target object, demonstrating the bidirectional coupling between visual working memory and perceptual processing. PMID:25228628

  13. Dynamic interactions between visual working memory and saccade target selection.

    Science.gov (United States)

    Schneegans, Sebastian; Spencer, John P; Schöner, Gregor; Hwang, Seongmin; Hollingworth, Andrew

    2014-09-16

    Recent psychophysical experiments have shown that working memory for visual surface features interacts with saccadic motor planning, even in tasks where the saccade target is unambiguously specified by spatial cues. Specifically, a match between a memorized color and the color of either the designated target or a distractor stimulus influences saccade target selection, saccade amplitudes, and latencies in a systematic fashion. To elucidate these effects, we present a dynamic neural field model in combination with new experimental data. The model captures the neural processes underlying visual perception, working memory, and saccade planning relevant to the psychophysical experiment. It consists of a low-level visual sensory representation that interacts with two separate pathways: a spatial pathway implementing spatial attention and saccade generation, and a surface feature pathway implementing color working memory and feature attention. Due to bidirectional coupling between visual working memory and feature attention in the model, the working memory content can indirectly exert an effect on perceptual processing in the low-level sensory representation. This in turn biases saccadic movement planning in the spatial pathway, allowing the model to quantitatively reproduce the observed interaction effects. The continuous coupling between representations in the model also implies that modulation should be bidirectional, and model simulations provide specific predictions for complementary effects of saccade target selection on visual working memory. These predictions were empirically confirmed in a new experiment: Memory for a sample color was biased toward the color of a task-irrelevant saccade target object, demonstrating the bidirectional coupling between visual working memory and perceptual processing. © 2014 ARVO.

  14. Gaia Space Mission and Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Zwitter, Tomaž, E-mail: tomaz.zwitter@fmf.uni-lj.si [Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana (Slovenia)

    2017-11-15

    Quasars are often considered to be point-like objects. This is largely true and allows for an excellent alignment of the optical positional reference frame of the ongoing ESA mission Gaia with the International Celestial Reference Frame. But presence of optical jets in quasars can cause shifts of the optical photo-centers at levels detectable by Gaia. Similarly, motion of emitting blobs in the jet can be detected as proper motion shifts. Gaia's measurements of spectral energy distribution for around a million distant quasars is useful to determine their redshifts and to assess their variability on timescales from hours to years. Spatial resolution of Gaia allows to build a complete magnitude limited sample of strongly lensed quasars. The mission had its first public data release in September 2016 and is scheduled to have the next and much more comprehensive one in April 2018. Here we briefly review the capabilities and current results of the mission. Gaia's unique contributions to the studies of quasars are already being published, a highlight being a discovery of a number of quasars with optical jets.

  15. Targets of balancing selection in the human genome

    DEFF Research Database (Denmark)

    Andrés, Aida M; Hubisz, Melissa J; Indap, Amit

    2009-01-01

    Balancing selection is potentially an important biological force for maintaining advantageous genetic diversity in populations, including variation that is responsible for long-term adaptation to the environment. By serving as a means to maintain genetic variation, it may be particularly relevant...... to maintaining phenotypic variation in natural populations. Nevertheless, its prevalence and specific targets in the human genome remain largely unknown. We have analyzed the patterns of diversity and divergence of 13,400 genes in two human populations using an unbiased single-nucleotide polymorphism data set......, a genome-wide approach, and a method that incorporates demography in neutrality tests. We identified an unbiased catalog of genes with signatures of long-term balancing selection, which includes immunity genes as well as genes encoding keratins and membrane channels; the catalog also shows enrichment...

  16. Far infrared peculiar behavior of quasars

    International Nuclear Information System (INIS)

    Liu Yulin; Liu Jiying

    1988-09-01

    Many quasars possibly have nebulous envelopes with far infrared radiation. These nebulosities may be similar to fuzz in the optical region in morphology. These quasars have many properties in common. (author). Refs, 3 figs

  17. The statistics of radio emission from quasars

    International Nuclear Information System (INIS)

    Peacock, J.A.; Miller, L.; Longair, M.S.; Edinburgh Univ.

    1986-01-01

    The radio properties of quasars have traditionally been discussed in terms of the radio-to-optical flux-density ratio R, implying a correlation between emission in these wavebands. It is here shown that, for bright quasars, this apparent correlation is largely due to an abrupt change in the radio properties of the quasar population near absolute magnitude Msub(B)=-24. It is suggested that this change in due to the existence of two classes of quasar with differing host galaxies: a proportion of quasars brighter than Msub(B)approx.=-24 lie in elliptical galaxies and thus generate powerful radio sources, while elliptical galaxies with weaker nuclear quasar components are classified as N-galaxies rather than quasars; quasars fainter than Msub(B)approx.=-24 lie in spiral galaxies and thus are high-luminosity analogues of radio-quiet Seyfert galaxies. (author)

  18. Positive-negative-selection-mediated gene targeting in rice

    Directory of Open Access Journals (Sweden)

    Zenpei eShimatani

    2015-01-01

    Full Text Available Gene targeting (GT refers to the designed modification of genomic sequence(s through homologous recombination (HR. GT is a powerful tool both for the study of gene function and for molecular breeding. However, in transformation of higher plants, non-homologous end joining (NHEJ occurs overwhelmingly in somatic cells, masking HR-mediated GT. Positive-negative selection (PNS is an approach for finding HR-mediated GT events because it can eliminate NHEJ effectively by expression of a negative-selection marker gene. In rice—a major crop worldwide—reproducible PNS-mediated GT of endogenous genes has now been successfully achieved. The procedure is based on strong PNS using diphtheria toxin A-fragment as a negative marker, and has succeeded in the directed modification of several endogenous rice genes in various ways. In addition to gene knock-outs and knock-ins, a nucleotide substitution in a target gene was also achieved recently. This review presents a summary of the development of the rice PNS system, highlighting its advantages. Different types of gene modification and gene editing aimed at developing new plant breeding technology (NPBT based on PNS are discussed.

  19. SDSS J1254+0846: A BINARY QUASAR CAUGHT IN THE ACT OF MERGING

    International Nuclear Information System (INIS)

    Green, Paul J.; Cox, Thomas J.; Aldcroft, Thomas L.; Myers, Adam D.; Barkhouse, Wayne A.; Mulchaey, John S.; Bennert, Vardha N.

    2010-01-01

    We present the first luminous, spatially resolved binary quasar that clearly inhabits an ongoing galaxy merger. SDSS J125455.09+084653.9 and SDSS J125454.87+084652.1 (SDSS J1254+0846 hereafter) are two luminous z = 0.44 radio-quiet quasars, with a radial velocity difference of just 215 km s -1 , separated on the sky by 21 kpc in a disturbed host galaxy merger showing obvious tidal tails. The pair was targeted as part of a complete sample of binary quasar candidates with small transverse separations drawn from SDSS DR6 photometry. We present follow-up optical imaging which shows broad, symmetrical tidal arm features spanning some 75 kpc at the quasars' redshift. Previously, the triggering of two quasars during a merger had only been hypothesized but our observations provide strong evidence of such an event. SDSS J1254+0846, as a face-on, pre-coalescence merger hosting two luminous quasars separated by a few dozen kpc, provides a unique opportunity to probe quasar activity in an ongoing gas-rich merger. Numerical modeling suggests that the system consists of two massive disk galaxies prograde to their mutual orbit, caught during the first passage of an active merger. This demonstrates rapid black hole growth during the early stages of a merger between galaxies with pre-existing bulges. Neither of the two luminous nuclei show significant intrinsic absorption by gas or dust in our optical or X-ray observations, illustrating that not all merging quasars will be in an obscured, ultraluminous phase. We find that the Eddington ratio for the fainter component B is rather normal, while for the A component L/L Edd is quite (>3σ) high compared to quasars of similar luminosity and redshift, possibly evidence for strong merger-triggered accretion. More such mergers should be identifiable at higher redshifts using binary quasars as tracers.

  20. Counts of low-Redshift SDSS quasar candidates

    International Nuclear Information System (INIS)

    Zeljko Ivezic

    2004-01-01

    We analyze the counts of low-redshift quasar candidates selected using nine-epoch SDSS imaging data. The co-added catalogs are more than 1 mag deeper than single-epoch SDSS data, and allow the selection of low-redshift quasar candidates using UV-excess and also variability techniques. The counts of selected candidates are robustly determined down to g = 21.5. This is about 2 magnitudes deeper than the position of a change in the slope of the counts reported by Boyle (and others) (1990, 2000) for a sample selected by UV-excess, and questioned by Hawkins and Veron (1995), who utilized a variability-selected sample. Using SDSS data, we confirm a change in the slope of the counts for both UV-excess and variability selected samples, providing strong support for the Boyle (and others) results

  1. Dust reddened quasars in first and UKIDSS: Beyond the tip of the iceberg

    Energy Technology Data Exchange (ETDEWEB)

    Glikman, Eilat [Department of Physics, Middlebury College, Middlebury, VT 05753 (United States); Urrutia, Tanya [Leibniz Institut fr Astrophysik, An der Sternwarte 16, D-14482 Potsdam (Germany); Lacy, Mark [National Radio Astronomy Observatory, Charlottesville, VA (United States); Djorgovski, S. G.; Mahabal, Ashish; Graham, Matthew [California Institute of Technology, Pasadena, CA 91125 (United States); Urry, Meg [Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520-8121 (United States); Croom, Scott [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Ge, Jian, E-mail: eglikman@middlebury.edu [Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611 (United States)

    2013-12-01

    We present the results of a pilot survey to find dust-reddened quasars by matching the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio catalog to the UKIDSS near-infrared survey and using optical data from Sloan Digital Sky Survey to select objects with very red colors. The deep K-band limit provided by UKIDSS allows for finding more heavily reddened quasars at higher redshifts as compared with previous work using FIRST and Two Micron All Sky Survey (2MASS). We selected 87 candidates with K ≤ 17.0 from the UKIDSS Large Area Survey (LAS) First Data Release (DR1), which covers 190 deg{sup 2}. These candidates reach up to ∼1.5 mag below the 2MASS limit and obey the color criteria developed to identify dust-reddened quasars. We have obtained 61 spectroscopic observations in the optical and/or near-infrared, as well as classifications in the literature, and have identified 14 reddened quasars with E(B – V) > 0.1, including 3 at z > 2. We study the infrared properties of the sample using photometry from the Wide-Field Infrared Survey Explorer and find that infrared colors improve the efficiency of red quasar selection, removing many contaminants in an infrared-to-optical color-selected sample alone. The highest-redshift quasars (z ≳ 2) are only moderately reddened, with E(B – V) ∼ 0.2-0.3. We find that the surface density of red quasars rises sharply with faintness, comprising up to 17% of blue quasars at the same apparent K-band flux limit. We estimate that to reach more heavily reddened quasars (i.e., E(B – V) ≳ 0.5) at z > 2 and a depth of K = 17, we would need to survey at least ∼2.5 times more area.

  2. DISCLOSING THE RADIO LOUDNESS DISTRIBUTION DICHOTOMY IN QUASARS: AN UNBIASED MONTE CARLO APPROACH APPLIED TO THE SDSS-FIRST QUASAR SAMPLE

    Energy Technology Data Exchange (ETDEWEB)

    Balokovic, M. [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Smolcic, V. [Argelander-Institut fuer Astronomie, Auf dem Hugel 71, D-53121 Bonn (Germany); Ivezic, Z. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Zamorani, G. [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Schinnerer, E. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Kelly, B. C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States)

    2012-11-01

    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 {+-} 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.

  3. DISCLOSING THE RADIO LOUDNESS DISTRIBUTION DICHOTOMY IN QUASARS: AN UNBIASED MONTE CARLO APPROACH APPLIED TO THE SDSS-FIRST QUASAR SAMPLE

    International Nuclear Information System (INIS)

    Baloković, M.; Smolčić, V.; Ivezić, Ž.; Zamorani, G.; Schinnerer, E.; Kelly, B. C.

    2012-01-01

    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 ± 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.

  4. VizieR Online Data Catalog: UV-bright quasars (Syphers+, 2009)

    Science.gov (United States)

    Syphers, D.; Anderson, S. F.; Zheng, W.; Haggard, D.; Meiksin, A.; Schneider, D. P.; York, D. G.

    2010-03-01

    Absorption along quasar sightlines remains among the most sensitive direct measures of HeII reionization in much of the intergalactic medium (IGM). Until recently, fewer than a half-dozen unobscured quasar sightlines suitable for the HeII Gunn-Peterson test were known; although these handful demonstrated great promise, the small sample size limited confidence in cosmological inferences. We have recently added nine more such clean HeII quasars, exploiting Sloan Digital Sky Survey (SDSS) quasar samples, broadband ultraviolet (UV) imaging from Galaxy Evolution Explorer (GALEX), and high-yield UV spectroscopic confirmations from Hubble Space Telescope (HST). Here we markedly expand this approach by cross-correlating SDSS DR7 and GALEX GR4+5 to catalog 428 SDSS and 165 other quasars with z>2.78 having likely (~70%) GALEX detections, suggesting they are bright into the far-UV. Reconnaissance HST Cycle 16 Supplemental prism data for 29 of these new quasar-GALEX matches spectroscopically confirm 17 as indeed far-UV bright. At least 10 of these confirmations have clean sightlines all the way down to HeII Lyα, substantially expanding the number of known clean HeII quasars, and reaffirming the order of magnitude enhanced efficiency of our selection technique. Combined confirmations from this and our past programs yield more than 20 HeII quasars, quintupling the sample. These provide substantial progress toward a sample of HeII quasar sightlines large enough, and spanning a sufficient redshift range, to enable statistical IGM studies that may avoid individual object peculiarity and sightline variance. Our expanded catalog of hundreds of high-likelihood far-UV-bright QSOs additionally will be useful for understanding the extreme-UV properties of the quasars themselves. (2 data files).

  5. The SDSS view of the Palomar-Green bright quasar survey

    Energy Technology Data Exchange (ETDEWEB)

    Jester, Sebastian; Schneider, Donald P.; Richards, Gordon T.; Green, Richard F.; Schmidt, Maarten; Hall, Patrick B.; Strauss, Michael A.; Vanden Berk, Daniel E.; Stoughton, Chris; Gunn, James E.; Brinkmann, Jon; Kent, Stephen M.; Smith, J.Allyn; Tucker, Douglas, L.; Yanny, Brian; /Fermilab /Penn State U., Astron. Astrophys. /Princeton U.

    2005-02-01

    The author investigates the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing with imaging and spectroscopy from the Sloan Digital Sky Survey. A comparison of SDSS and PG photometry of both stars and quasars reveals the need to apply a color and magnitude recalibration to the PG data. Using the SDSS photometric catalog, they define the PG's parent sample of objects that are not main-sequence stars and simulate the selection of objects from this parent sample using the PG photometric criteria and errors. This simulation shows that the effective U-B cut in the PG survey is U-B < -0.71, implying a color-related incompleteness. As the color distribution of bright quasars peaks near U-B = -0.7 and the 2-{sigma} error in U-B is comparable to the full width of the color distribution of quasars, the color incompleteness of the BQS is approximately 50% and essentially random with respect to U-B color for z < 0.5. There is however, a bias against bright quasars at 0.5 < z < 1, which is induced by the color-redshift relation of quasars (although quasars at z > 0.5 are inherently rare in bright surveys in any case). They find no evidence for any other systematic incompleteness when comparing the distributions in color, redshift, and FIRST radio properties of the BQS and a BQS-like subsample of the SDSS quasar sample. However, the application of a bright magnitude limit biases the BQS toward the inclusion of objects which are blue in g-i, in particular compared to the full range of g-i colors found among the i-band limited SDSS quasars, and even at i-band magnitudes comparable to those of the BQS objects.

  6. Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Rumbaugh, N.; Shen, Yue; Morganson, Eric; Liu, Xin; Banerji, M.; McMahon, R. G.; Abdalla, F. B.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; D’Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Doel, P.; Frieman, J.; García-Bellido, J.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Menanteau, F.; Plazas, A. A.; Reil, K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sheldon, E.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Walker, A. R.; Wester, W.

    2018-02-20

    We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey (SDSS) and 3-Year Dark Energy Survey (DES) imaging, which provide light curves spanning more than 15 years. We identified ~1000 EVQs with a maximum g band magnitude change of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have L_bol~10^45-10^47 erg/s and L/L_Edd~0.01-1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of ~30-50% among all g<~22 quasars over a baseline of ~15 years. These EVQs are good candidates for so-called "changing-look quasars", where a spectral transition between the two types of quasars (broad-line and narrow-line) is observed between the dim and bright states. We performed detailed multi-wavelength, spectral and variability analyses for the EVQs and compared to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggest that internal processes associated with accretion are the main driver for the observed extreme long-term variability. However, despite their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low accretion rates, where the accretion flow is more likely to experience instabilities that drive the factor of few changes in flux on multi-year timescales.

  7. A DISTANT QUASAR'S BRILLIANT LIGHT

    Science.gov (United States)

    2002-01-01

    The arrow in this image, taken by a ground-based telescope, points to a distant quasar, the brilliant core of an active galaxy residing billions of light-years from Earth. As light from this faraway object travels across space, it picks up information on galaxies and the vast clouds of material between galaxies as it moves through them. The Space Telescope Imaging Spectrograph aboard NASA's Hubble Space Telescope decoded the quasar's light to find the spectral 'fingerprints' of highly ionized (energized) oxygen, which had mixed with invisible clouds of hydrogen in intergalactic space. The quasar's brilliant beam pierced at least four separate filaments of the invisible hydrogen laced with the telltale oxygen. The presence of oxygen between the galaxies implies there are huge quantities of hydrogen in the universe. Credits: WIYN Telescope at Kitt Peak National Observatory in Arizona. The telescope is owned and operated by the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories.

  8. CD133, Selectively Targeting the Root of Cancer

    Directory of Open Access Journals (Sweden)

    Jörg U. Schmohl

    2016-05-01

    Full Text Available Cancer stem cells (CSC are capable of promoting tumor initiation and self-renewal, two important hallmarks of carcinoma formation. This population comprises a small percentage of the tumor mass and is highly resistant to chemotherapy, causing the most difficult problem in the field of cancer research, drug refractory relapse. Many CSC markers have been reported. One of the most promising and perhaps least ubiquitous is CD133, a membrane-bound pentaspan glycoprotein that is frequently expressed on CSC. There is evidence that directly targeting CD133 with biological drugs might be the most effective way to eliminate CSC. We have investigated two entirely unrelated, but highly effective approaches for selectively targeting CD133. The first involves using a special anti-CD133 single chain variable fragment (scFv to deliver a catalytic toxin. The second utilizes this same scFv to deliver components of the immune system. In this review, we discuss the development and current status of these CD133 associated biological agents. Together, they show exceptional promise by specific and efficient CSC elimination.

  9. Superconducting cosmic string evolution of quasars

    International Nuclear Information System (INIS)

    Liu Yulin.

    1988-09-01

    The quasars may have been undergoing two evolutionary processes after they formed. As a result of the string loops shrinking at the first stage, the luminosities of the quasars increased gradually up to their maximum value at the redshift z ∼ 2, after then the second evolutionary stage began and the luminosity reduced. This result can be fitted by luminosity counting of quasars. Observable limit of quasars can be obtained naturally. Many phenomena, such as radiomorphology, density distribution between fuzz structure and broad line region and rotational curve may also originate from the first evolutionary stage of quasars as cosmic string. (author). 10 refs

  10. Proper motions and distances of quasars

    International Nuclear Information System (INIS)

    Varshni, Y.P.

    1982-01-01

    The author's theory that quasars are stars raises the question of their proper motions. From the evidence presented in a previous paper, it is hypothesised that planetary nuclei and quasars are related objects and that their distributions in the galaxy are not very different. Proper motions of 30 quasars, calculated from existing measurements, are discussed. It is shown that three of these, namely PHL 1033, LB 8956 and LB 8991, have proper motions comparable to the largest proper motion known amongst the planetary nuclei. From this it is estimated that these three quasars lie within a few hundred parsecs from the sun. The evidence presented in a previous paper and the present one clearly supports the theory that quasars are stars. The possibility of using the interstellar K and H lines as distance indicators of quasars is discussed and the available evidence summarised. The desirability of determining more accurate values of the proper motions of quasars is emphasised. (Auth.)

  11. Axions and polarisation of quasars

    International Nuclear Information System (INIS)

    Payez, A.; Cudell, J. R.; Hutsemekers, D.

    2008-01-01

    We present results showing that, thanks to axion-photon mixing in external magnetic fields, it is actually possible to produce an effect similar to the one needed to explain the large-scale coherent orientations of quasar polarisation vectors in visible light that have been observed in some regions of the sky

  12. IRAS 10479 - 2808: a quasar

    International Nuclear Information System (INIS)

    Clowes, R.G.; Leggett, S.K.; Savage, A.

    1991-01-01

    The IRAS point source 10479-2808 is a quasar with B J ∼ 16 and z = 0.190. It is not in the Parkes and Molonglo radio catalogues. At the resolution of the UK and ESO Schmidt telescopes it appears to be star-like, with no sign of surrounding fuzz or interactions; it is probably optically variable. (author)

  13. First Discoveries of z > 6 Quasars with the DECam Legacy Survey and UKIRT Hemisphere Survey

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Feige; Yang, Jinyi; Wu, Xue-Bing; Yang, Qian; Li, Zefeng [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Fan, Xiaohui; McGreer, Ian D.; Ding, Jiani; Green, Richard [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Bian, Fuyan [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); Li, Jiang-Tao [Department of Astronomy, University of Michigan, 311 West Hall, 1085 S. University Avenue, Ann Arbor, MI, 48109 (United States); Dey, Arjun [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Dye, Simon [School of Physics and Astronomy, Nottingham University, University Park, Nottingham, NG7 2RD (United Kingdom); Findlay, Joseph R.; Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); James, David [Cerro Tololo Inter-American Observatory, Casilla 603 La Serena (Chile); Jiang, Linhua [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Lang, Dustin [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario, M5S 3H4 (Canada); Lawrence, Andy; Ross, Nicholas P. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom); and others

    2017-04-10

    We present the first discoveries from a survey of z ≳ 6 quasars using imaging data from the DECam Legacy Survey (DECaLS) in the optical, the UKIRT Deep Infrared Sky Survey (UKIDSS) and a preliminary version of the UKIRT Hemisphere Survey (UHS) in the near-IR, and ALLWISE in the mid-IR. DECaLS will image 9000 deg{sup 2} of sky down to z {sub AB} ∼ 23.0, and UKIDSS and UHS will map the northern sky at 0 < decl. < +60°, reaching J {sub VEGA} ∼ 19.6 (5- σ ). The combination of these data sets allows us to discover quasars at redshift z ≳ 7 and to conduct a complete census of the faint quasar population at z ≳ 6. In this paper, we report on the selection method of our search, and on the initial discoveries of two new, faint z ≳ 6 quasars and one new z = 6.63 quasar in our pilot spectroscopic observations. The two new z ∼ 6 quasars are at z = 6.07 and z = 6.17 with absolute magnitudes at rest-frame wavelength 1450 Å being M {sub 1450} = −25.83 and M {sub 1450} = −25.76, respectively. These discoveries suggest that we can find quasars close to or fainter than the break magnitude of the Quasar Luminosity Function (QLF) at z ≳ 6. The new z = 6.63 quasar has an absolute magnitude of M {sub 1450} = −25.95. This demonstrates the potential of using the combined DECaLS and UKIDSS/UHS data sets to find z ≳ 7 quasars. Extrapolating from previous QLF measurements, we predict that these combined data sets will yield ∼200 z ∼ 6 quasars to z {sub AB} < 21.5, ∼1000 z ∼ 6 quasars to z {sub AB} < 23, and ∼30 quasars at z > 6.5 to J {sub VEGA} < 19.5.

  14. Target and Tissue Selectivity Prediction by Integrated Mechanistic Pharmacokinetic-Target Binding and Quantitative Structure Activity Modeling.

    Science.gov (United States)

    Vlot, Anna H C; de Witte, Wilhelmus E A; Danhof, Meindert; van der Graaf, Piet H; van Westen, Gerard J P; de Lange, Elizabeth C M

    2017-12-04

    Selectivity is an important attribute of effective and safe drugs, and prediction of in vivo target and tissue selectivity would likely improve drug development success rates. However, a lack of understanding of the underlying (pharmacological) mechanisms and availability of directly applicable predictive methods complicates the prediction of selectivity. We explore the value of combining physiologically based pharmacokinetic (PBPK) modeling with quantitative structure-activity relationship (QSAR) modeling to predict the influence of the target dissociation constant (K D ) and the target dissociation rate constant on target and tissue selectivity. The K D values of CB1 ligands in the ChEMBL database are predicted by QSAR random forest (RF) modeling for the CB1 receptor and known off-targets (TRPV1, mGlu5, 5-HT1a). Of these CB1 ligands, rimonabant, CP-55940, and Δ 8 -tetrahydrocanabinol, one of the active ingredients of cannabis, were selected for simulations of target occupancy for CB1, TRPV1, mGlu5, and 5-HT1a in three brain regions, to illustrate the principles of the combined PBPK-QSAR modeling. Our combined PBPK and target binding modeling demonstrated that the optimal values of the K D and k off for target and tissue selectivity were dependent on target concentration and tissue distribution kinetics. Interestingly, if the target concentration is high and the perfusion of the target site is low, the optimal K D value is often not the lowest K D value, suggesting that optimization towards high drug-target affinity can decrease the benefit-risk ratio. The presented integrative structure-pharmacokinetic-pharmacodynamic modeling provides an improved understanding of tissue and target selectivity.

  15. Weak Hard X-Ray Emission from Broad Absorption Line Quasars: Evidence for Intrinsic X-Ray Weakness

    DEFF Research Database (Denmark)

    Luo, B.; Brandt, W. N.; Alexander, D. M.

    2014-01-01

    We report NuSTAR observations of a sample of six X-ray weak broad absorption line (BAL) quasars. These targets, at z = 0.148-1.223, are among the optically brightest and most luminous BAL quasars known at z 330 times weaker than...... expected for typical quasars. Our results from a pilot NuSTAR study of two low-redshift BAL quasars, a Chandra stacking analysis of a sample of high-redshift BAL quasars, and a NuSTAR spectral analysis of the local BAL quasar Mrk 231 have already suggested the existence of intrinsically X-ray weak BAL...... quasars, i.e., quasars not emitting X-rays at the level expected from their optical/UV emission. The aim of the current program is to extend the search for such extraordinary objects. Three of the six new targets are weakly detected by NuSTAR with ≲ 45 counts in the 3-24 keV band, and the other three...

  16. A gravitationally lensed quasar discovered in OGLE

    Science.gov (United States)

    Kostrzewa-Rutkowska, Zuzanna; Kozłowski, Szymon; Lemon, Cameron; Anguita, T.; Greiner, J.; Auger, M. W.; Wyrzykowski, Ł.; Apostolovski, Y.; Bolmer, J.; Udalski, A.; Szymański, M. K.; Soszyński, I.; Poleski, R.; Pietrukowicz, P.; Skowron, J.; Mróz, P.; Ulaczyk, K.; Pawlak, M.

    2018-05-01

    We report the discovery of a new gravitationally lensed quasar (double) from the Optical Gravitational Lensing Experiment (OGLE) identified inside the ˜670deg2 area encompassing the Magellanic Clouds. The source was selected as one of ˜60 `red W1 - W2' mid-infrared objects from WISE and having a significant amount of variability in OGLE for both two (or more) nearby sources. This is the first detection of a gravitational lens, where the discovery is made `the other way around', meaning we first measured the time delay between the two lensed quasar images of -132 Technology Telescope spectra. The spectral energy distribution (SED) fitting with the fixed source redshift provided the estimate of the lensing galaxy redshift of z ≈ 0.9 ± 0.2 (90 per cent CL), while its type is more likely to be elliptical (the SED-inferred and lens-model stellar mass is more likely present in ellipticals) than spiral (preferred redshift by the lens model).

  17. Discovery of a very Lyman-α-luminous quasar at z = 6.62.

    Science.gov (United States)

    Koptelova, Ekaterina; Hwang, Chorng-Yuan; Yu, Po-Chieh; Chen, Wen-Ping; Guo, Jhen-Kuei

    2017-02-02

    Distant luminous quasars provide important information on the growth of the first supermassive black holes, their host galaxies and the epoch of reionization. The identification of quasars is usually performed through detection of their Lyman-α line redshifted to 0.9 microns at z > 6.5. Here, we report the discovery of a very Lyman-α luminous quasar, PSO J006.1240 + 39.2219 at redshift z = 6.618, selected based on its red colour and multi-epoch detection of the Lyman-α emission in a single near-infrared band. The Lyman-α line luminosity of PSO J006.1240 + 39.2219 is unusually high and estimated to be 0.8 × 10 12 Solar luminosities (about 3% of the total quasar luminosity). The Lyman-α emission of PSO J006.1240 + 39.2219 shows fast variability on timescales of days in the quasar rest frame, which has never been detected in any of the known high-redshift quasars. The high luminosity of the Lyman-α line, its narrow width and fast variability resemble properties of local Narrow-Line Seyfert 1 galaxies which suggests that the quasar is likely at the active phase of the black hole growth accreting close or even beyond the Eddington limit.

  18. Q0000-398 is a high-redshift quasar with a large angular size

    International Nuclear Information System (INIS)

    Gearhart, M.R.; Pacht, E.

    1977-01-01

    A study is described, using the three-element interferrometer at the National Radio Astronomy Observatory, West Virginia, to investigate whether any quasars exist that might be radio sources. It was found that Q0000-398 appeared to be a quasar of high red shift and large angular size. The interferrometer was operated with a 300-1200-1500 m baseline configuration at 2695 MHz. The radio map for Q0000-398 is shown, and has two weak components separated by 134 +- 40 arc s. If these components are associated with the optical object this quasar has the largest known angular size for its red shift value. The results reported for Q0000-398 and other quasars having considerable angular extent demonstrate the importance of considering radio selection effects in the angular diameter-red shift relationship, and since any radio selection effects are removed when quasars are selected optically, more extensive mapping programs should be undertaken, looking particularly for large scale structure around optically selected high-z quasars. (U.K.)

  19. THE HIGH A{sub V} Quasar Survey: Reddened Quasi-Stellar Objects selected from optical/near-infrared photometry. II

    Energy Technology Data Exchange (ETDEWEB)

    Krogager, J.-K.; Fynbo, J. P. U.; Vestergaard, M. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark); Geier, S. [Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain); Venemans, B. P. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Ledoux, C. [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19 (Chile); Møller, P. [European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching bei München (Germany); Noterdaeme, P. [Institut d’Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, F-75014 Paris (France); Kangas, T.; Pursimo, T.; Smirnova, O. [Nordic Optical Telescope, Apartado 474, E-38700 Santa Cruz de La Palma (Spain); Saturni, F. G. [Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Väisäläntie 20, 21500 Piikkiö (Finland)

    2015-03-15

    Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are reddened by dust either in their host galaxies or in intervening absorber galaxies are to a large degree missed by optical color selection criteria like the ones used by the Sloan Digital Sky Survey (SDSS). To overcome this bias against red QSOs, we employ a combined optical and near-infrared (near-IR) color selection. In this paper, we present a spectroscopic follow-up campaign of a sample of red candidate QSOs which were selected from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). The spectroscopic data and SDSS/UKIDSS photometry are supplemented by mid-infrared photometry from the Wide-field Infrared Survey Explorer. In our sample of 159 candidates, 154 (97%) are confirmed to be QSOs. We use a statistical algorithm to identify sightlines with plausible intervening absorption systems and identify nine such cases assuming dust in the absorber similar to Large Magellanic Cloud sightlines. We find absorption systems toward 30 QSOs, 2 of which are consistent with the best-fit absorber redshift from the statistical modeling. Furthermore, we observe a broad range in SED properties of the QSOs as probed by the rest-frame 2 μm flux. We find QSOs with a strong excess as well as QSOs with a large deficit at rest-frame 2 μm relative to a QSO template. Potential solutions to these discrepancies are discussed. Overall, our study demonstrates the high efficiency of the optical/near-IR selection of red QSOs.

  20. On The Dark Side of Quasar Evolution

    OpenAIRE

    Menou, Kristen; Haiman, Zoltan

    2004-01-01

    Recent improved determinations of the mass density rho_BH of supermassive black holes (SMBHs) in the local universe have allowed accurate comparisons of rho_BH with the amount of light received from past quasar activity. These comparisons support the notion that local SMBHs are ``dead quasars'' and yield a value epsilon >~ 0.1 for the average radiative efficiency of cosmic SMBH accretion. BH coalescences may represent an important component of the quasar mass assembly and yet not produce any ...

  1. Effects of Mode of Target Task Selection on Learning about Plants in a Mobile Learning Environment: Effortful Manual Selection versus Effortless QR-Code Selection

    Science.gov (United States)

    Gao, Yuan; Liu, Tzu-Chien; Paas, Fred

    2016-01-01

    This study compared the effects of effortless selection of target plants using quick respond (QR) code technology to effortful manual search and selection of target plants on learning about plants in a mobile device supported learning environment. In addition, it was investigated whether the effectiveness of the 2 selection methods was…

  2. New background quasars in the vicinity of the Andromeda Galaxy discovered with the Guoshoujing Telescope (LAMOST)

    International Nuclear Information System (INIS)

    Huo Zhiying; Liu Xiaowei; Yuan Haibo; Zhang Huihua; Zhang Huawei; Zhao Yongheng; Chen Jianjun; Bai Zhongrui; Zhang Haotong; Yan Hongliang; Ren Juanjuan; Sun Shiwei; GarcIa-Benito, Ruben; Xiang Maosheng; Zhang Yong; Li Yeping; Lu Qishuai; Wang You; Ni Jijun; Wang Hai

    2010-01-01

    We present preliminary analyses of spectra of quasar candidates in two Guoshoujing Telescope (GSJT, formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope - LAMOST) test fields near M 31 where one is close to the optical center of the disk and the other is towards the northeastern outskirts of the halo, obtained during the early stage of the GSJT commissioning in the last season of 2009. Both fields contain background low-redshift quasar candidates selected from the SDSS photometry. In total, 14 new quasars with redshifts up to 2 and i magnitudes between 16.7 and 19.2, are discovered, including 7 within the 2.5 0 central region of M 31. We briefly discuss the potential applications of these newly discovered bright quasars. (editor's recommendation)

  3. Clustering of quasars in a wide luminosity range at redshift 4 with Subaru Hyper Suprime-Cam Wide-field imaging

    Science.gov (United States)

    He, Wanqiu; Akiyama, Masayuki; Bosch, James; Enoki, Motohiro; Harikane, Yuichi; Ikeda, Hiroyuki; Kashikawa, Nobunari; Kawaguchi, Toshihiro; Komiyama, Yutaka; Lee, Chien-Hsiu; Matsuoka, Yoshiki; Miyazaki, Satoshi; Nagao, Tohru; Nagashima, Masahiro; Niida, Mana; Nishizawa, Atsushi J.; Oguri, Masamune; Onoue, Masafusa; Oogi, Taira; Ouchi, Masami; Schulze, Andreas; Shirasaki, Yuji; Silverman, John D.; Tanaka, Manobu M.; Tanaka, Masayuki; Toba, Yoshiki; Uchiyama, Hisakazu; Yamashita, Takuji

    2018-01-01

    We examine the clustering of quasars over a wide luminosity range, by utilizing 901 quasars at \\overline{z}_phot˜ 3.8 with -24.73 Strategic Program (HSC-SSP) S16A Wide2 date release and 342 more luminous quasars at 3.4 Digital Sky Survey that fall in the HSC survey fields. We measure the bias factors of two quasar samples by evaluating the cross-correlation functions (CCFs) between the quasar samples and 25790 bright z ˜ 4 Lyman break galaxies in M1450 < -21.25 photometrically selected from the HSC dataset. Over an angular scale of 10.0" to 1000.0", the bias factors are 5.93+1.34-1.43 and 2.73+2.44-2.55 for the low- and high-luminosity quasars, respectively, indicating no significant luminosity dependence of quasar clustering at z ˜ 4. It is noted that the bias factor of the luminous quasars estimated by the CCF is smaller than that estimated by the auto-correlation function over a similar redshift range, especially on scales below 40.0". Moreover, the bias factor of the less-luminous quasars implies the minimal mass of their host dark matter halos is 0.3-2 × 1012 h-1 M⊙, corresponding to a quasar duty cycle of 0.001-0.06.

  4. The most luminous heavily obscured quasars have a high merger fraction: morphological study of wise -selected hot dust-obscured galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Lulu; Gao, Ying; Zhang, Dandan; Jiang, Xiaoming; Wu, Qiaoqian; Yang, Jun; Li, Zhao [Shandong Provincial Key Lab of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Science, Shandong University, Weihai 264209 (China); Han, Yunkun [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Fang, Guanwen, E-mail: llfan@sdu.edu.cn, E-mail: hanyk@ynao.ac.cn [Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003 (China)

    2016-05-10

    Previous studies have shown that Wide-field Infrared Survey Explorer -selected hyperluminous, hot dust-obscured galaxies (Hot DOGs) are powered by highly dust-obscured, possibly Compton-thick active galactic nuclei (AGNs). High obscuration provides us a good chance to study the host morphology of the most luminous AGNs directly. We analyze the host morphology of 18 Hot DOGs at z ∼ 3 using Hubble Space Telescope /WFC3 imaging. We find that Hot DOGs have a high merger fraction (62 ± 14%). By fitting the surface brightness profiles, we find that the distribution of Sérsic indices in our Hot DOG sample peaks around 2, which suggests that most Hot DOGs have transforming morphologies. We also derive the AGN bolometric luminosity (∼10{sup 14} L {sub ⊙}) of our Hot DOG sample by using IR spectral energy distributions decomposition. The derived merger fraction and AGN bolometric luminosity relation is well consistent with the variability-based model prediction. Both the high merger fraction in an IR-luminous AGN sample and relatively low merger fraction in a UV/optical-selected, unobscured AGN sample can be expected in the merger-driven evolutionary model. Finally, we conclude that Hot DOGs are merger-driven and may represent a transit phase during the evolution of massive galaxies, transforming from the dusty starburst-dominated phase to the unobscured QSO phase.

  5. NO OVERDENSITY OF LYMAN-ALPHA EMITTING GALAXIES AROUND A QUASAR AT z  ∼ 5.7

    International Nuclear Information System (INIS)

    Mazzucchelli, C.; Bañados, E.; Decarli, R.; Farina, E. P.; Venemans, B. P.; Walter, F.; Overzier, R.

    2017-01-01

    Bright quasars, observed when the universe was less than one billion years old ( z  > 5.5), are known to host massive black holes (∼10 9 M ⊙ ) and are thought to reside in the center of massive dark matter overdensities. In this picture, overdensities of galaxies are expected around high-redshift quasars. However, observations based on the detection of Lyman-break galaxies (LBGs) around these quasars do not offer a clear picture: this may be due to the uncertain redshift constraints of LBGs, which are solely selected through broadband filters. To circumvent such uncertainties, we here perform a search for Lyman-alpha emitting galaxies (LAEs) in the field of the quasar PSO J215.1512–16.0417 at z  ∼ 5.73, through narrowband deep imaging with FORS2 at the Very Large Telescope. We study an area of 37 arcmin 2 , i.e., ∼206 comoving Mpc 2 at the redshift of the quasar. We find no evidence of an overdensity of LAEs in the quasar field with respect to blank-field studies. Possible explanations for these findings may be that our survey volume is too small, or that the strong ionizing radiation from the quasar hinders galaxy formation in its immediate proximity. Another possibility is that these quasars are not situated in the dense environments predicted by some simulations.

  6. NO OVERDENSITY OF LYMAN-ALPHA EMITTING GALAXIES AROUND A QUASAR AT z  ∼ 5.7

    Energy Technology Data Exchange (ETDEWEB)

    Mazzucchelli, C.; Bañados, E.; Decarli, R.; Farina, E. P.; Venemans, B. P.; Walter, F. [Max Planck Institute für Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Overzier, R. [Observatório Nacional, Rua José Cristino, 77. CEP 20921-400, São Cristóvão, Rio de Janeiro-RJ (Brazil)

    2017-01-01

    Bright quasars, observed when the universe was less than one billion years old ( z  > 5.5), are known to host massive black holes (∼10{sup 9} M {sub ⊙}) and are thought to reside in the center of massive dark matter overdensities. In this picture, overdensities of galaxies are expected around high-redshift quasars. However, observations based on the detection of Lyman-break galaxies (LBGs) around these quasars do not offer a clear picture: this may be due to the uncertain redshift constraints of LBGs, which are solely selected through broadband filters. To circumvent such uncertainties, we here perform a search for Lyman-alpha emitting galaxies (LAEs) in the field of the quasar PSO J215.1512–16.0417 at z  ∼ 5.73, through narrowband deep imaging with FORS2 at the Very Large Telescope. We study an area of 37 arcmin{sup 2}, i.e., ∼206 comoving Mpc{sup 2} at the redshift of the quasar. We find no evidence of an overdensity of LAEs in the quasar field with respect to blank-field studies. Possible explanations for these findings may be that our survey volume is too small, or that the strong ionizing radiation from the quasar hinders galaxy formation in its immediate proximity. Another possibility is that these quasars are not situated in the dense environments predicted by some simulations.

  7. Is 1146+111B, C a lensed quasar or a quasar pair

    International Nuclear Information System (INIS)

    Huchra, J.P.

    1986-01-01

    It has been speculated that the quasar pair 1146+B, C are two bright images of a single quasar produced by a gravitational lens. The author reports additional observations of these objects, made with an ultraviolet-sensitive spectrograph on the Multiple Mirror Telescope. The ultraviolet spectra of the two quasars are different. There are also different velocity shifts between the quasars as measured by the C III] and Mg II lines. Although it is impossible to rule out the lensing hypothesis, these observations increase the probability that these objects are just two quasars at nearly the same redshift. (author)

  8. Two more, bright, z > 6 quasars from VST ATLAS and WISE

    Science.gov (United States)

    Chehade, B.; Carnall, A. C.; Shanks, T.; Diener, C.; Fumagalli, M.; Findlay, J. R.; Metcalfe, N.; Hennawi, J.; Leibler, C.; Murphy, D. N. A.; Prochaska, J. X.; Irwin, M. J.; Gonzalez-Solares, E.

    2018-03-01

    Recently, Carnall et al. discovered two bright high redshift quasars using the combination of the VST ATLAS and WISE surveys. The technique involved using the 3-D colour plane i - z: z - W1: W1 - W2 with the WISE W1(3.4 micron) and W2 (4.5 micron) bands taking the place of the usual NIR J band to help decrease stellar dwarf contamination. Here we report on our continued search for 5.7 6 quasars, VST-ATLAS J158.6938-14.4211 at z = 6.07 and J332.8017-32.1036 at z = 6.32 with magnitudes of zAB = 19.4 and 19.7 mag respectively. J158.6938-14.4211 was confirmed by Keck LRIS observations and J332.8017-32.1036 was confirmed by ESO NTT EFOSC-2 observations. Here we present VLT X-shooter Visible and NIR spectra for the four ATLAS quasars. We have further independently rediscovered two z > 5.7 quasars previously found by the VIKING/KiDS and PanSTARRS surveys. This means that in ATLAS we have now discovered a total of six quasars in our target 5.7 ATLAS quasars.

  9. Quasars: Active nuclei of young galaxies

    Science.gov (United States)

    Komberg, B. V.

    1980-01-01

    The hypothetical properties of 'young' galaxies and possible methods of observing them are discussed. It is proposed that star formation first takes place in the central regions of protogalaxies which may appear as quasar-like objects. An evolutionary scheme is outlined in which the radio quasars are transformed in time into the nuclei of radio galaxies.

  10. Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

    Science.gov (United States)

    Rumbaugh, N.; Shen, Yue; Morganson, Eric; Liu, Xin; Banerji, M.; McMahon, R. G.; Abdalla, F. B.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; D’Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Doel, P.; Frieman, J.; García-Bellido, J.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Menanteau, F.; Plazas, A. A.; Reil, K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sheldon, E.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Walker, A. R.; Wester, W.; (DES Collaboration

    2018-02-01

    We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey and 3 Year Dark Energy Survey imaging, which provide light curves spanning more than 15 years. We identified ∼1000 EVQs with a maximum change in g-band magnitude of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have L bol ∼ 1045–1047 erg s‑1 and L/L Edd ∼ 0.01–1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of ∼30%–50% among all g≲ 22 quasars over a baseline of ∼15 yr. We performed detailed multi-wavelength, spectral, and variability analyses for the EVQs and compared them to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggests that internal processes associated with accretion are the main driver for the observed extreme long-term variability. However, despite their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low rates, where the accretion flow is more likely to experience instabilities that drive the changes in flux by a factor of a few on multi-year timescales.

  11. BROAD ABSORPTION LINE DISAPPEARANCE ON MULTI-YEAR TIMESCALES IN A LARGE QUASAR SAMPLE

    Energy Technology Data Exchange (ETDEWEB)

    Filiz Ak, N.; Brandt, W. N.; Schneider, D. P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Hall, P. B. [Department of Physics and Astronomy, York University, 4700 Keele St., Toronto, Ontario M3J 1P3 (Canada); Anderson, S. F.; Gibson, R. R. [Astronomy Department, University of Washington, Seattle, WA 98195 (United States); Lundgren, B. F. [Department of Physics, Yale University, New Haven, CT 06511 (United States); Myers, A. D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Petitjean, P. [Institut d' Astrophysique de Paris, Universite Paris 6, F-75014, Paris (France); Ross, Nicholas P. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States); Shen Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States); York, D. G. [Department of Astronomy and Astrophysics, and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Bizyaev, D.; Brinkmann, J.; Malanushenko, E.; Oravetz, D. J.; Pan, K.; Simmons, A. E. [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); Weaver, B. A., E-mail: nfilizak@astro.psu.edu [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States)

    2012-10-01

    We present 21 examples of C IV broad absorption line (BAL) trough disappearance in 19 quasars selected from systematic multi-epoch observations of 582 bright BAL quasars (1.9 < z < 4.5) by the Sloan Digital Sky Survey-I/II (SDSS-I/II) and SDSS-III. The observations span 1.1-3.9 yr rest-frame timescales, longer than have been sampled in many previous BAL variability studies. On these timescales, Almost-Equal-To 2.3% of C IV BAL troughs disappear and Almost-Equal-To 3.3% of BAL quasars show a disappearing trough. These observed frequencies suggest that many C IV BAL absorbers spend on average at most a century along our line of sight to their quasar. Ten of the 19 BAL quasars showing C IV BAL disappearance have apparently transformed from BAL to non-BAL quasars; these are the first reported examples of such transformations. The BAL troughs that disappear tend to be those with small-to-moderate equivalent widths, relatively shallow depths, and high outflow velocities. Other non-disappearing C IV BALs in those nine objects having multiple troughs tend to weaken when one of them disappears, indicating a connection between the disappearing and non-disappearing troughs, even for velocity separations as large as 10,000-15,000 km s{sup -1}. We discuss possible origins of this connection including disk-wind rotation and changes in shielding gas.

  12. Phylogenetic Analyses of Quasars and Galaxies

    Science.gov (United States)

    Fraix-Burnet, Didier; D'Onofrio, Mauro; Marziani, Paola

    2017-10-01

    Phylogenetic approaches have proven to be useful in astrophysics. We have recently published a Maximum Parsimony (or cladistics) analysis on two samples of 215 and 85 low-z quasars (z phylogeny of quasars may be represented by the ontogeny of their central black hole, i.e. the increase of the black hole mass. However these exciting results are based on a small sample of low-z quasars, so that the work must be extended. We are here faced with two difficulties. The first one is the current lack of a larger sample with similar observables. The second one is the prohibitive computation time to perform a cladistic analysis on more that about one thousand objects. We show in this paper an experimental strategy on about 1500 galaxies to get around this difficulty. Even if it not related to the quasar study, it is interesting by itself and opens new pathways to generalize the quasar findings.

  13. Antimicrobial Peptide-PNA Conjugates Selectively Targeting Bacterial Genes

    Science.gov (United States)

    2013-07-22

    antibacterial therapy. Initial publications suggest that conjugates of cell penetrating peptides and PNA’s can overcome the barrier in transporting ...Zhou, Y., Hou, Z., Meng, J., and Luo, X. Targeting RNA polymerase primary σ70 as a therapeutic strategy against methicillin - resistant ... Staphylococcus aureus by antisense peptide nucleic acid. PLoS One. 2012; 7(1):e29886. 2. Good, L., Sandberg, R., Larsson, O., Nielsen, P.E., and Wahlestedt, C

  14. Selective phosphodiesterase inhibitors: a promising target for cognition enhancement

    OpenAIRE

    Reneerkens, Olga A. H.; Rutten, Kris; Steinbusch, Harry W. M.; Blokland, Arjan; Prickaerts, Jos

    2008-01-01

    Rationale One of the major complaints most people face during aging is an impairment in cognitive functioning. This has a negative impact on the quality of daily life and is even more prominent in patients suffering from neurodegenerative and psychiatric disorders including Alzheimer?s disease, schizophrenia, and depression. So far, the majority of cognition enhancers are generally targeting one particular neurotransmitter system. However, recently phosphodiesterases (PDEs) have gained increa...

  15. The Halo Occupation Distribution of obscured quasars: revisiting the unification model

    Science.gov (United States)

    Mitra, Kaustav; Chatterjee, Suchetana; DiPompeo, Michael A.; Myers, Adam D.; Zheng, Zheng

    2018-06-01

    We model the projected angular two-point correlation function (2PCF) of obscured and unobscured quasars selected using the Wide-field Infrared Survey Explorer (WISE), at a median redshift of z ˜ 1 using a five parameter Halo Occupation Distribution (HOD) parametrization, derived from a cosmological hydrodynamic simulation by Chatterjee et al. The HOD parametrization was previously used to model the 2PCF of optically selected quasars and X-ray bright active galactic nuclei (AGNs) at z ˜ 1. The current work shows that a single HOD parametrization can be used to model the population of different kinds of AGN in dark matter haloes suggesting the universality of the relationship between AGN and their host dark matter haloes. Our results show that the median halo mass of central quasar hosts increases from optically selected (4.1^{+0.3}_{-0.4} × 10^{12} h^{-1} M_{⊙}) and infra-red (IR) bright unobscured populations (6.3^{+6.2}_{-2.3} × 10^{12} h^{-1} M_{⊙}) to obscured quasars (10.0^{+2.6}_{-3.7} × 10^{12} h^{-1} M_{⊙}), signifying an increase in the degree of clustering. The projected satellite fractions also increase from optically bright to obscured quasars and tend to disfavour a simple `orientation only' theory of active galactic nuclei unification. Our results also show that future measurements of the small-scale clustering of obscured quasars can constrain current theories of galaxy evolution where quasars evolve from an IR-bright obscured phase to the optically bright unobscured phase.

  16. Evaluating gaze-based interface tools to facilitate point-and-select tasks with small targets

    DEFF Research Database (Denmark)

    Skovsgaard, Henrik; Mateo, Julio C.; Hansen, John Paulin

    2011-01-01

    -and-select tasks. We conducted two experiments comparing the performance of dwell, magnification and zoom methods in point-and-select tasks with small targets in single- and multiple-target layouts. Both magnification and zoom showed higher hit rates than dwell. Hit rates were higher when using magnification than...

  17. A comparative study of fuzzy target selection methods in direct marketing

    NARCIS (Netherlands)

    Costa Sousa, da J.M.; Kaymak, U.; Madeira, S.

    2002-01-01

    Target selection in direct marketing is an important data mining problem for which fuzzy modeling can be used. The paper compares several fuzzy modeling techniques applied to target selection based on recency, frequency and monetary value measures. The comparison uses cross validation applied to

  18. The z=0.0912 and z=0.2212 damped Ly alpha galaxies along the sight line toward the quasar OI 363

    NARCIS (Netherlands)

    Turnshek, DA; Rao, S; Nestor, D; Lane, W; Monier, E; Bergeron, J; Smette, A

    2001-01-01

    New optical and infrared observations along the sight line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding quasars selectively observed because they were known to be located behind gas-rich galaxies and systems which lack confirming UV spectroscopic observations of the

  19. Selection of phage-displayed accessible recombinant targeted antibodies (SPARTA): methodology and applications.

    Science.gov (United States)

    D'Angelo, Sara; Staquicini, Fernanda I; Ferrara, Fortunato; Staquicini, Daniela I; Sharma, Geetanjali; Tarleton, Christy A; Nguyen, Huynh; Naranjo, Leslie A; Sidman, Richard L; Arap, Wadih; Bradbury, Andrew Rm; Pasqualini, Renata

    2018-05-03

    We developed a potentially novel and robust antibody discovery methodology, termed selection of phage-displayed accessible recombinant targeted antibodies (SPARTA). This combines an in vitro screening step of a naive human antibody library against known tumor targets, with in vivo selections based on tumor-homing capabilities of a preenriched antibody pool. This unique approach overcomes several rate-limiting challenges to generate human antibodies amenable to rapid translation into medical applications. As a proof of concept, we evaluated SPARTA on 2 well-established tumor cell surface targets, EphA5 and GRP78. We evaluated antibodies that showed tumor-targeting selectivity as a representative panel of antibody-drug conjugates (ADCs) and were highly efficacious. Our results validate a discovery platform to identify and validate monoclonal antibodies with favorable tumor-targeting attributes. This approach may also extend to other diseases with known cell surface targets and affected tissues easily isolated for in vivo selection.

  20. THE HALO OCCUPATION DISTRIBUTION OF SDSS QUASARS

    International Nuclear Information System (INIS)

    Richardson, Jonathan; Chatterjee, Suchetana; Nagai, Daisuke; Zheng Zheng; Shen Yue

    2012-01-01

    We present an estimate of the projected two-point correlation function (2PCF) of quasars in the Sloan Digital Sky Survey (SDSS) over the full range of one- and two-halo scales, 0.02 h –1 Mpc p –1 Mpc. This was achieved by combining data from SDSS DR7 on large scales and Hennawi et al. (with appropriate statistical corrections) on small scales. Our combined clustering sample is the largest spectroscopic quasar clustering sample to date, containing ∼48, 000 quasars in the redshift range 0.4 ∼ sat = (7.4 ± 1.4) × 10 –4 , be satellites in dark matter halos. At z ∼ 1.4, the median masses of the host halos of central and satellite quasars are constrained to be M cen = 4.1 +0.3 –0.4 × 10 12 h –1 M ☉ and M sat = 3.6 +0.8 –1.0 × 10 14 h –1 M ☉ , respectively. To investigate the redshift evolution of the quasar-halo relationship, we also perform HOD modeling of the projected 2PCF measured by Shen et al. for SDSS quasars with median redshift 3.2. We find tentative evidence for an increase in the mass scale of quasar host halos—the inferred median mass of halos hosting central quasars at z ∼ 3.2 is M cen = 14.1 +5.8 –6.9 × 10 12 h –1 M ☉ . The cutoff profiles of the mean occupation functions of central quasars reveal that quasar luminosity is more tightly correlated with halo mass at higher redshifts. The average quasar duty cycle around the median host halo mass is inferred to be f q = 7.3 +0.6 –1.5 × 10 –4 at z ∼ 1.4 and f q = 8.6 +20.4 –7.2 × 10 –2 at z ∼ 3.2. We discuss the implications of our results for quasar evolution and quasar-galaxy co-evolution.

  1. The folate receptor as a molecular target for tumor-selective radionuclide delivery

    International Nuclear Information System (INIS)

    Ke, C.-Y.; Mathias, Carla J.; Green, Mark A.

    2003-01-01

    The cell-membrane folate receptor is a potential molecular target for tumor-selective drug delivery, including radiolabeled folate-chelate conjugates for diagnostic imaging. We review here some background on the folate receptor as tumor-associated molecular target for drug delivery, and briefly survey the literature on tumor-targeting with radiolabeled folate-chelate conjugates

  2. In vitro Selection and Interaction Studies of a DNA Aptamer Targeting Protein A

    OpenAIRE

    Stoltenburg, Regina; Schubert, Thomas; Strehlitz, Beate

    2015-01-01

    A new DNA aptamer targeting Protein A is presented. The aptamer was selected by use of the FluMag-SELEX procedure. The SELEX technology (Systematic Evolution of Ligands by EXponential enrichment) is widely applied as an in vitro selection and amplification method to generate target-specific aptamers and exists in various modified variants. FluMag-SELEX is one of them and is characterized by the use of magnetic beads for target immobilization and fluorescently labeled oligonucleotides for moni...

  3. Signal Transduction and Molecular Targets of Selected Flavonoids

    Science.gov (United States)

    Bode, Ann M.

    2013-01-01

    Abstract Significance: Diet exerts a major influence on the risk for developing cancer and heart disease. Food factors such as flavonoids are alleged to protect cells from premature aging and disease by shielding DNA, proteins, and lipids from oxidative damage. Recent Advances: Our work has focused on clarifying the effects of dietary components on cancer cell proliferation and tumor growth, discovering mechanisms to explain the effects, and identifying the specific molecular targets of these compounds. Our strategy for identifying specific molecular targets of phytochemicals involves the use of supercomputer technology combined with protein crystallography, molecular biology, and experimental laboratory verification. Critical Issues: One of the greatest challenges for scientists is to reduce the accumulation of distortion and half truths reported in the popular media regarding the health benefits of certain foods or food supplements. The use of these is not new, but interest has increased dramatically because of perceived health benefits that are presumably acquired without unpleasant side effects. Flavonoids are touted to exert many beneficial effects in vitro. However, whether they can produce these effects in vivo is disputed. Future Directions: The World Health Organization indicates that one third of all cancer deaths are preventable and that diet is closely linked to prevention. Based on this idea and epidemiological findings, attention has centered on dietary phytochemicals as an effective intervention in cancer development. However, an unequivocal link between diet and cancer has not been established. Thus, identifying cancer preventive dietary agents with specific molecular targets is essential to move forward toward successful cancer prevention. Antioxid. Redox Signal. 19, 163–180. PMID:23458437

  4. Epigenetic Editing: targeted rewriting of epigenetic marks to modulate expression of selected target genes.

    NARCIS (Netherlands)

    de Groote, M.L.; Verschure, P.J.; Rots, M.G.

    2012-01-01

    Despite significant advances made in epigenetic research in recent decades, many questions remain unresolved, especially concerning cause and consequence of epigenetic marks with respect to gene expression modulation (GEM). Technologies allowing the targeting of epigenetic enzymes to predetermined

  5. Epigenetic Editing : targeted rewriting of epigenetic marks to modulate expression of selected target genes

    NARCIS (Netherlands)

    de Groote, Marloes L.; Verschure, Pernette J.; Rots, Marianne G.

    2012-01-01

    Despite significant advances made in epigenetic research in recent decades, many questions remain unresolved, especially concerning cause and consequence of epigenetic marks with respect to gene expression modulation (GEM). Technologies allowing the targeting of epigenetic enzymes to predetermined

  6. QUASAR CLUSTERING FROM SDSS DR5: DEPENDENCES ON PHYSICAL PROPERTIES

    International Nuclear Information System (INIS)

    Shen Yue; Strauss, Michael A.; Lin, Yen-Ting; Bahcall, Neta A.; Ross, Nicholas P.; Schneider, Donald P.; Vanden Berk, Daniel E.; Hall, Patrick B.; Richards, Gordon T.; Weinberg, David H.; Shankar, Francesco; Connolly, Andrew J.; Fan Xiaohui; Hennawi, Joseph F.; Brunner, Robert J.

    2009-01-01

    Using a homogenous sample of 38,208 quasars with a sky coverage of ∼4000 deg. 2 drawn from the Sloan Digital Sky Survey Data Release Five quasar catalog, we study the dependence of quasar clustering on luminosity, virial black hole (BH) mass, quasar color, and radio loudness. At z 13 h -1 M sun , compared to ∼2 x 10 12 h -1 M sun for radio-quiet quasar hosts at z ∼ 1.5.

  7. Targeting cancer cells using 3-bromopyruvate for selective cancer treatment

    Directory of Open Access Journals (Sweden)

    Hussam H Baghdadi

    2017-01-01

    Full Text Available Cancer treatment deserves more research efforts despite intensive conventional treatment modalities for many types of malignancies. Metastasis and resistance to chemotherapy and radiotherapy receive a lot of global research efforts. The current advances in cancer biology may improve targeting the critical metabolic differences that distinguish cancer cells from normal cells. Cancer cells are highly glycolytic for energy production, exhibit the Warburg effect, establish aggressive acidic microenvironment, maintain cancer stem cells, exhibit resistance to chemotherapy, have low antioxidant systems but different ΔΨm (delta psi, mitochondrial transmembrane potential, express P-glycoprotein for multidrug resistance, upregulate glucose transporters and monocarboxylate transporters and are under high steady-state reactive oxygen species conditions. Normal cells differ in all these aspects. Lactate produced through the Warburg effect helps cancer metastasis. Targeting glycolysis reactions for energy production in cancer cells seems promising in decreasing the proliferation and metastasis of cancer cells. 3-bromopyruvate makes use of cancer biology in treating cancer cells, cancer stem cells and preventing metastasis in human cancer as discussed in this review. Updated advances are analyzed here, which include research analysis of background, experience, readings in the field of cancer biology, oncology and biochemistry.

  8. Targeting ticks for control of selected hemoparasitic diseases of cattle.

    Science.gov (United States)

    Kocan, K M

    1995-03-01

    Development in and transmission of hemoparasites by tick vectors are phenomena closely synchronized with the tick feeding cycle. In all known life cycles, initial infection of tick tissues occurs in midgut epithelial cells and transmission is effected as ticks feed after parasites have developed and multiplied in salivary glands. Many factors reviewed affect development and transmission of hemoparasites by ticks including age of ticks, artificial temperature, climate and/or season, tick stage or sex, hemoparasite variation, concurrent infection of ticks with other pathogens, host cell susceptibility, transovarial transmission, effect of hemoparasites on tick biology, and the effect of infecting parasitemia level in cattle on infection rates in ticks. Four hemoparasites of cattle, Anaplasma marginale, Cowdria ruminantium, Theileria parva, and Babesia spp., are all dependent on ticks for biological transmission. Babesia is transmitted transovarially whereas the other three are transmitted transstadially. Mechanical transfer of infective blood via fomites and mouthparts of biting arthropods is also a major means of transmission for Anaplasma marginale but not of the others. Potential control methods for hemoparasites that target parasites as they are developing in their respective tick hosts include tick control, vaccines (against ticks and parasites), and drugs (against ticks and parasites). Successful application of control strategies will be dependent upon thorough understanding of parasite developmental cycles, biology of the tick vectors and the immune response of cattle to ticks and to hemoparasites. The most effective control measures will be those that are targeted against both ticks and the hemoparasites they vector.

  9. Phylogenetic Analyses of Quasars and Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Fraix-Burnet, Didier [University Grenoble Alpes, CNRS, IPAG, Grenoble (France); D' Onofrio, Mauro [Osservatorio Astronomico di Padova (INAF), Padua (Italy); Marziani, Paola, E-mail: didier.fraix-burnet@univ-grenoble-alpes.fr [Dipartimento di Fisica e Astronomia, Università di Padova, Padua (Italy)

    2017-10-10

    Phylogenetic approaches have proven to be useful in astrophysics. We have recently published a Maximum Parsimony (or cladistics) analysis on two samples of 215 and 85 low-z quasars (z < 0.7) which offer a satisfactory coverage of the Eigenvector 1-derived main sequence. Cladistics is not only able to group sources radiating at higher Eddington ratios, to separate radio-quiet (RQ) and radio-loud (RL) quasars and properly distinguishes core-dominated and lobe-dominated quasars, but it suggests a black hole mass threshold for powerful radio emission as already proposed elsewhere. An interesting interpretation from this work is that the phylogeny of quasars may be represented by the ontogeny of their central black hole, i.e. the increase of the black hole mass. However these exciting results are based on a small sample of low-z quasars, so that the work must be extended. We are here faced with two difficulties. The first one is the current lack of a larger sample with similar observables. The second one is the prohibitive computation time to perform a cladistic analysis on more that about one thousand objects. We show in this paper an experimental strategy on about 1,500 galaxies to get around this difficulty. Even if it not related to the quasar study, it is interesting by itself and opens new pathways to generalize the quasar findings.

  10. HUBBLE CAPTURES MERGER BETWEEN QUASAR AND GALAXY

    Science.gov (United States)

    2002-01-01

    This NASA Hubble Space Telescope image shows evidence fo r a merger between a quasar and a companion galaxy. This surprising result might require theorists to rethink their explanations for the nature of quasars, the most energetic objects in the universe. The bright central object is the quasar itself, located several billion light-years away. The two wisps on the (left) of the bright central object are remnants of a bright galaxy that have been disrupted by the mutual gravitational attraction between the quasar and the companion galaxy. This provides clear evidence for a merger between the two objects. Since their discovery in 1963, quasars (quasi-stellar objects) have been enigmatic because they emit prodigious amounts of energy from a very compact source. The most widely accepted model is that a quasar is powered by a supermassive black hole in the core of a galaxy. These new observations proved a challenge for theorists as no current models predict the complex quasar interactions unveiled by Hubble. The image was taken with the Wide Field Planetary Camera-2. Credit: John Bahcall, Institute for Advanced Study, NASA.

  11. Phylogenetic Analyses of Quasars and Galaxies

    International Nuclear Information System (INIS)

    Fraix-Burnet, Didier; D'Onofrio, Mauro; Marziani, Paola

    2017-01-01

    Phylogenetic approaches have proven to be useful in astrophysics. We have recently published a Maximum Parsimony (or cladistics) analysis on two samples of 215 and 85 low-z quasars (z < 0.7) which offer a satisfactory coverage of the Eigenvector 1-derived main sequence. Cladistics is not only able to group sources radiating at higher Eddington ratios, to separate radio-quiet (RQ) and radio-loud (RL) quasars and properly distinguishes core-dominated and lobe-dominated quasars, but it suggests a black hole mass threshold for powerful radio emission as already proposed elsewhere. An interesting interpretation from this work is that the phylogeny of quasars may be represented by the ontogeny of their central black hole, i.e. the increase of the black hole mass. However these exciting results are based on a small sample of low-z quasars, so that the work must be extended. We are here faced with two difficulties. The first one is the current lack of a larger sample with similar observables. The second one is the prohibitive computation time to perform a cladistic analysis on more that about one thousand objects. We show in this paper an experimental strategy on about 1,500 galaxies to get around this difficulty. Even if it not related to the quasar study, it is interesting by itself and opens new pathways to generalize the quasar findings.

  12. The Hunt for Red Quasars: Luminous Obscured Black Hole Growth Unveiled in the Stripe 82 X-Ray Survey

    Science.gov (United States)

    LaMassa, Stephanie M.; Glikman, Eilat; Brusa, Marcella; Rigby, Jane R.; Tasnim Ananna, Tonima; Stern, Daniel; Lira, Paulina; Urry, C. Megan; Salvato, Mara; Alexandroff, Rachael; Allevato, Viola; Cardamone, Carolin; Civano, Francesca; Coppi, Paolo; Farrah, Duncan; Komossa, S.; Lanzuisi, Giorgio; Marchesi, Stefano; Richards, Gordon; Trakhtenbrot, Benny; Treister, Ezequiel

    2017-10-01

    We present results of a ground-based near-infrared campaign with Palomar TripleSpec, Keck NIRSPEC, and Gemini GNIRS to target two samples of reddened active galactic nucleus (AGN) candidates from the 31 deg2 Stripe 82 X-ray survey. One sample, which is ˜89% complete to Kprogram, and is selected to have red R - K colors (> 4, Vega). The fainter sample (K> 17, Vega) represents a pilot program to follow-up four sources from a parent sample of 34 that are not detected in the single-epoch SDSS catalog and have WISE quasar colors. All 12 sources are broad-line AGNs (at least one permitted emission line has an FWHM exceeding 1300 km s-1) and span a redshift range 0.59 0.5), and a greater percentage have high X-ray luminosities ({L}{{X},{full}}> {10}44 erg s-1). Such outflows and high luminosities may be consistent with the paradigm that reddened broad-line AGNs represent a transitory phase in AGN evolution as described by the major merger model for black hole growth. Results from our pilot program demonstrate proof of concept that our selection technique is successful in discovering reddened quasars at z> 1 missed by optical surveys.

  13. Quantitative modeling of selective lysosomal targeting for drug design

    DEFF Research Database (Denmark)

    Trapp, Stefan; Rosania, G.; Horobin, R.W.

    2008-01-01

    log K ow. These findings were validated with experimental results and by a comparison to the properties of antimalarial drugs in clinical use. For ten active compounds, nine were predicted to accumulate to a greater extent in lysosomes than in other organelles, six of these were in the optimum range...... predicted by the model and three were close. Five of the antimalarial drugs were lipophilic weak dibasic compounds. The predicted optimum properties for a selective accumulation of weak bivalent bases in lysosomes are consistent with experimental values and are more accurate than any prior calculation...

  14. Dissecting patterns of preparatory activity in the frontal eye fields during pursuit target selection.

    Science.gov (United States)

    Raghavan, Ramanujan T; Joshua, Mati

    2017-10-01

    We investigated the composition of preparatory activity of frontal eye field (FEF) neurons in monkeys performing a pursuit target selection task. In response to the orthogonal motion of a large and a small reward target, monkeys initiated pursuit biased toward the direction of large reward target motion. FEF neurons exhibited robust preparatory activity preceding movement initiation in this task. Preparatory activity consisted of two components, ramping activity that was constant across target selection conditions, and a flat offset in firing rates that signaled the target selection condition. Ramping activity accounted for 50% of the variance in the preparatory activity and was linked most strongly, on a trial-by-trial basis, to pursuit eye movement latency rather than to its direction or gain. The offset in firing rates that discriminated target selection conditions accounted for 25% of the variance in the preparatory activity and was commensurate with a winner-take-all representation, signaling the direction of large reward target motion rather than a representation that matched the parameters of the upcoming movement. These offer new insights into the role that the frontal eye fields play in target selection and pursuit control. They show that preparatory activity in the FEF signals more strongly when to move rather than where or how to move and suggest that structures outside the FEF augment its contributions to the target selection process. NEW & NOTEWORTHY We used the smooth eye movement pursuit system to link between patterns of preparatory activity in the frontal eye fields and movement during a target selection task. The dominant pattern was a ramping signal that did not discriminate between selection conditions and was linked, on trial-by-trial basis, to movement latency. A weaker pattern was composed of a constant signal that discriminated between selection conditions but was only weakly linked to the movement parameters. Copyright © 2017 the American

  15. Metformin selectively targets redox control of complex I energy transduction

    Directory of Open Access Journals (Sweden)

    Amy R. Cameron

    2018-04-01

    Full Text Available Many guanide-containing drugs are antihyperglycaemic but most exhibit toxicity, to the extent that only the biguanide metformin has enjoyed sustained clinical use. Here, we have isolated unique mitochondrial redox control properties of metformin that are likely to account for this difference. In primary hepatocytes and H4IIE hepatoma cells we found that antihyperglycaemic diguanides DG5-DG10 and the biguanide phenformin were up to 1000-fold more potent than metformin on cell signalling responses, gluconeogenic promoter expression and hepatocyte glucose production. Each drug inhibited cellular oxygen consumption similarly but there were marked differences in other respects. All diguanides and phenformin but not metformin inhibited NADH oxidation in submitochondrial particles, indicative of complex I inhibition, which also corresponded closely with dehydrogenase activity in living cells measured by WST-1. Consistent with these findings, in isolated mitochondria, DG8 but not metformin caused the NADH/NAD+ couple to become more reduced over time and mitochondrial deterioration ensued, suggesting direct inhibition of complex I and mitochondrial toxicity of DG8. In contrast, metformin exerted a selective oxidation of the mitochondrial NADH/NAD+ couple, without triggering mitochondrial deterioration. Together, our results suggest that metformin suppresses energy transduction by selectively inducing a state in complex I where redox and proton transfer domains are no longer efficiently coupled. Keywords: Diabetes, Metformin, Mitochondria, NADH, NAD+

  16. Moderate resolution spectrophotometry of high redshift quasars

    Science.gov (United States)

    Schneider, Donald P.; Schmidt, Maarten; Gunn, James E.

    1991-01-01

    A uniform set of photometry and high signal-to-noise moderate resolution spectroscopy of 33 quasars with redshifts larger than 3.1 is presented. The sample consists of 17 newly discovered quasars (two with redshifts in excess of 4.4) and 16 sources drawn from the literature. The objects in this sample have r magnitudes between 17.4 and 21.4; their luminosities range from -28.8 to -24.9. Three of the 33 objects are broad absorption line quasars. A number of possible high redshift damped Ly-alpha systems were found.

  17. Targeting of phage particles towards endothelial cells by antibodies selected through a multi-parameter selection strategy.

    Science.gov (United States)

    Mandrup, Ole A; Lykkemark, Simon; Kristensen, Peter

    2017-02-10

    One of the hallmarks of cancer is sustained angiogenesis. Here, normal endothelial cells are activated, and their formation of new blood vessels leads to continued tumour growth. An improved patient condition is often observed when angiogenesis is prevented or normalized through targeting of these genomically stable endothelial cells. However, intracellular targets constitute a challenge in therapy, as the agents modulating these targets have to be delivered and internalized specifically to the endothelial cells. Selection of antibodies binding specifically to certain cell types is well established. It is nonetheless a challenge to ensure that the binding of antibodies to the target cell will mediate internalization. Previously selection of such antibodies has been performed targeting cancer cell lines; most often using either monovalent display or polyvalent display. In this article, we describe selections that isolate internalizing antibodies by sequential combining monovalent and polyvalent display using two types of helper phages, one which increases display valence and one which reduces background. One of the selected antibodies was found to mediate internalization into human endothelial cells, although our results confirms that the single stranded nature of the DNA packaged into phage particles may limit applications aimed at targeting nucleic acids in mammalian cells.

  18. Rhodacyanine derivative selectively targets cancer cells and overcomes tamoxifen resistance.

    Directory of Open Access Journals (Sweden)

    John Koren

    Full Text Available MKT-077, a rhodacyanine dye, was shown to produce cancer specific cell death. However, complications prevented the use of this compound beyond clinical trials. Here we describe YM-1, a derivative of MKT-077. We found that YM-1 was more cytotoxic and localized differently than MKT-077. YM-1 demonstrated this cytotoxicity across multiple cancer cell lines. This toxicity was limited to cancer cell lines; immortalized cell models were unaffected. Brief applications of YM-1 were found to be non-toxic. Brief treatment with YM-1 restored tamoxifen sensitivity to a refractory tamoxifen-resistant MCF7 cell model. This effect is potentially due to altered estrogen receptor alpha phosphorylation, an outcome precipitated by selective reductions in Akt levels (Akt/PKB. Thus, modifications to the rhodocyanine scaffold could potentially be made to improve efficacy and pharmacokinetic properties. Moreover, the impact on tamoxifen sensitivity could be a new utility for this compound family.

  19. Visual cells remember earlier applied target: plasticity of orientation selectivity.

    Directory of Open Access Journals (Sweden)

    Narcis Ghisovan

    Full Text Available BACKGROUND: A canonical proposition states that, in mature brain, neurons responsive to sensory stimuli are tuned to specific properties installed shortly after birth. It is amply demonstrated that that neurons in adult visual cortex of cats are orientation-selective that is they respond with the highest firing rates to preferred oriented stimuli. METHODOLOGY/PRINCIPAL FINDINGS: In anesthetized cats, prepared in a conventional fashion for single cell recordings, the present investigation shows that presenting a stimulus uninterruptedly at a non-preferred orientation for twelve minutes induces changes in orientation preference. Across all conditions orientation tuning curves were investigated using a trial by trial method. Contrary to what has been previously reported with shorter adaptation duration, twelve minutes of adaptation induces mostly attractive shifts, i.e. toward the adapter. After a recovery period allowing neurons to restore their original orientation tuning curves, we carried out a second adaptation which produced three major results: (1 more frequent attractive shifts, (2 an increase of their magnitude, and (3 an additional enhancement of responses at the new or acquired preferred orientation. Additionally, we also show that the direction of shifts depends on the duration of the adaptation: shorter adaptation in most cases produces repulsive shifts, whereas adaptation exceeding nine minutes results in attractive shifts, in the same unit. Consequently, shifts in preferred orientation depend on the duration of adaptation. CONCLUSION/SIGNIFICANCE: The supplementary response improvements indicate that neurons in area 17 keep a memory trace of the previous stimulus properties, thereby upgrading cellular performance. It also highlights the dynamic nature of basic neuronal properties in adult cortex since repeated adaptations modified both the orientation tuning selectivity and the response strength to the preferred orientation. These

  20. VizieR Online Data Catalog: Quasar luminosity function (Hawkins+, 1993)

    Science.gov (United States)

    Hawkins, M. R. S.; Veron, P.

    1994-11-01

    A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sigh of the 'break' found in the recent UVX sample of Boyle, Shanks & Peterson. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved. (1 data file).

  1. THE PROPERTIES OF QUASAR HOSTS AT THE PEAK OF THE QUASAR ACTIVITY

    International Nuclear Information System (INIS)

    Kotilainen, Jari K.; Falomo, Renato; Decarli, Roberto; Treves, Aldo; Uslenghi, Michela; Scarpa, Riccardo

    2009-01-01

    We present near-infrared imaging obtained with ESO VLT/ISAAC of a sample of 16 low luminosity radio-quiet quasars (RQQs) at the epoch around the peak of the quasar activity (2 2. The luminosity trend with a cosmic epoch resembles that observed for massive inactive galaxies, suggesting a similar star formation history. In particular, both quasar host galaxies and massive inactive galaxies appear mostly assembled already at the peak age of the quasar activity. This result is of key importance for testing the models of joint formation and evolution of galaxies and their active nuclei.

  2. A homogeneous catalogue of quasar candidates found with slitless spectroscopy

    International Nuclear Information System (INIS)

    Beauchemin, M.; Borra, E.F.; Edwards, G.

    1990-01-01

    This paper gives a list of all quasar candidates obtained from an automated computer search performed on 11 grens plates. The description of the main characteristics of the survey is given along with the latest improvements in the selection techniques. Particular attention has been paid to understanding and quantifying selection effects. This allows the construction of homogeneous samples having well-understood characteristics. The noteworthy aspect of our homogenization process is the correction that we apply to our probability classes in order to take into account the signal-to-noise differences; at a given magnitude, among plates of different limiting magnitudes. (author)

  3. Detection of baryon acoustic oscillations in the Lyman-α forests of BOSS quasar spectra

    International Nuclear Information System (INIS)

    Delubac, Timothee

    2013-01-01

    Baryon acoustic oscillations (BAO) form a standard ruler that can be used to constrain different cosmological models. This thesis reports the first measurement of the BAO feature in the correlation function of the transmitted flux fraction in the Lyman-α forests of high redshift quasars. This detection uses 89322 quasar spectra measured by the Baryon Oscillation Spectroscopic Survey (BOSS) of the third generation of the Sloan Digital Sky Survey (SDSS-III). Redshift of used quasars belong to the range 2.1≤z≤3.5. A peak in the correlation function is seen at 1.043"+"0"."0"2"1_-_0_._0_2_0 times the expected BAO peak position for a concordance ΛCDM model. In addition this thesis presents a new method of quasar selection through their variability. This method is applied to the Stripe 82 region where an important number of multi-epoch photometric data is available. On this region it achieves a quasar density of 30 deg"-"2 to be compared with the 18 deg"-"2 of usual color selections. (author) [fr

  4. In Vitro Selection and Characterization of DNA Aptamers to a Small Molecule Target.

    Science.gov (United States)

    Ruscito, Annamaria; McConnell, Erin M; Koudrina, Anna; Velu, Ranganathan; Mattice, Christopher; Hunt, Vernon; McKeague, Maureen; DeRosa, Maria C

    2017-12-14

    Aptamers, synthetic oligonucleotide-based molecular recognition probes, have found use in a wide array of biosensing technologies based on their tight and highly selective binding to a variety of molecular targets. However, the inherent challenges associated with the selection and characterization of aptamers for small molecule targets have resulted in their underrepresentation, despite the need for small molecule detection in fields such as medicine, the environment, and agriculture. This protocol describes the steps in the selection, sequencing, affinity characterization, and truncation of DNA aptamers that are specific for small molecule targets. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

  5. Discovery and first models of the quadruply lensed quasar SDSS J1433+6007

    Science.gov (United States)

    Agnello, Adriano; Grillo, Claudio; Jones, Tucker; Treu, Tommaso; Bonamigo, Mario; Suyu, Sherry H.

    2018-03-01

    We report the discovery of the quadruply lensed quasar SDSS J1433+6007 (RA = 14:33:22.8, Dec. = +60:07:13.44), mined in the SDSS DR12 photometric catalogues using a novel outlier-selection technique, without prior spectroscopic or ultraviolet excess information. Discovery data obtained at the Nordic Optical Telescope (La Palma) show nearly identical quasar spectra at zs = 2.737 ± 0.003 and four quasar images in a fold configuration, one of which sits on a blue arc, with maximum separation 3.6 arcsec. The deflector redshift is zl = 0.407 ± 0.002, from Keck-ESI spectra. We describe the selection procedure, discovery and follow-up, image positions and BVRi magnitudes, and first results and forecasts from lens model fit to the relative image positions.

  6. Optical spectra and radio properties of quasars

    International Nuclear Information System (INIS)

    Wills, B.J.

    1982-01-01

    Using high quality spectrophotometric scans obtained at the McDonald Observatory, and data from the literature the author shows that, for quasars, the relative strength of optical Fe II emission (the broad blended feature lambda4570) may be roughly inversely proportional to line widths (full width at half maximum, FWHM). A similar relation between the relative intensity of the UV Fe II blend between 2300 and 2600 A (the lambda2500 feature) and the widths of Mg II and Hβ is shown. She distinguishes between compact and extended radio sources and includes radio quiet quasars, Seyfert 1 galaxies and BLRG's. The quasars associated with extended radio sources have the broadest emission lines and the weakest Fe II, falling close to the region occupied by BLRG's which also have extended radio structure. Those quasars with strong Fe II and compact radio structure are most similar to the Seyfert 1 galaxies. (Auth.)

  7. Automatic Target Recognition: Statistical Feature Selection of Non-Gaussian Distributed Target Classes

    Science.gov (United States)

    2011-06-01

    implementing, and evaluating many feature selection algorithms. Mucciardi and Gose compared seven different techniques for choosing subsets of pattern...122 THIS PAGE INTENTIONALLY LEFT BLANK 123 LIST OF REFERENCES [1] A. Mucciardi and E. Gose , “A comparison of seven techniques for

  8. Dust in the Quasar Wind (Artist Concept)

    Science.gov (United States)

    2007-01-01

    Dusty grains -- including tiny specks of the minerals found in the gemstones peridot, sapphires and rubies -- can be seen blowing in the winds of a quasar, or active black hole, in this artist's concept. The quasar is at the center of a distant galaxy. Astronomers using NASA's Spitzer Space Telescope found evidence that such quasar winds might have forged these dusty particles in the very early universe. The findings are another clue in an ongoing cosmic mystery: where did all the dust in our young universe come from? Dust is crucial for efficient star formation as it allows the giant clouds where stars are born to cool quickly and collapse into new stars. Once a star has formed, dust is also needed to make planets and living creatures. Dust has been seen as far back as when the universe was less than a tenth of its current age, but how did it get there? Most dust in our current epoch forms in the winds of evolved stars that did not exist when the universe was young. Theorists had predicted that winds from quasars growing in the centers of distant galaxies might be a source of this dust. While the environment close to a quasar is too hot for large molecules like dust grains to survive, dust has been found in the cooler, outer regions. Astronomers now have evidence that dust is created in these outer winds. Using Spitzer's infrared spectrograph instrument, scientists found a wealth of dust grains in a quasar called PG2112+059 located at the center of a galaxy 8 billion light-years away. The grains - including corundum (sapphires and rubies); forsterite (peridot); and periclase (naturally occurring in marble) - are not typically found in galaxies without quasars, suggesting they might have been freshly formed in the quasar's winds.

  9. Coping with Atmospheric Turbulence in the Selection of Laser Hardening Technology for FCS Targeting Systems

    National Research Council Canada - National Science Library

    Pritchett, Timothy M

    2004-01-01

    ... by frequency-agile battlefield lasers at both long and short range. Evidently, the selection of sensor protection technologies for incorporation into the final targeting system will be based on their optical limiting performance under field conditions...

  10. The CTIO surveys for large redshift quasars

    International Nuclear Information System (INIS)

    Osmer, P.S.

    1978-01-01

    Lyman α emission in large redshift quasars is readily detectable on slitless spectrograms taken with an objective combination on the 4m telescope. This provides a new survey method, independent of color for finding radio-quiet quasars in large numbers. Surveys by Smith with the Curtis Schmidt and Hoag and Smith with the 4 m telescope, have produced more than 200 candidates with 1.5< z<3.5 and 16< m<21. Spectroscopic observations with the CTIO SIT vidicon system have been carried out for more than 50 of the candidates, with the result that the basic properties of the surveys are known. To date three 16th magnitude quasars with zapproximately2.2 and six quasars with 3.0< z<3.25 have been found. One of the most important uses of the surveys will be the determination of the surface and surface densities of large redshift quasars. A preliminary analysis of the data indicates that the space density of quasars is at least constant, if not increasing, over the interval 1.0< z<3.25. However, the Hoag-Smith sample has only one candidate with z<3.2.(Auth.)

  11. The control of attentional target selection in a colour/colour conjunction task

    OpenAIRE

    Berggren, Nick; Eimer, Martin

    2016-01-01

    To investigate the time course of attentional object selection processes in visual search tasks where targets are defined by a combination of features from the same dimension, we measured the N2pc component as an electrophysiological marker of attentional object selection during colour/colour conjunction search. In Experiment 1, participants searched for targets defined by a combination of two colours, while ignoring distractor objects that matched only one of these colours. Reliable N2pc com...

  12. Auditory Stream Segregation Improves Infants' Selective Attention to Target Tones Amid Distracters

    Science.gov (United States)

    Smith, Nicholas A.; Trainor, Laurel J.

    2011-01-01

    This study examined the role of auditory stream segregation in the selective attention to target tones in infancy. Using a task adapted from Bregman and Rudnicky's 1975 study and implemented in a conditioned head-turn procedure, infant and adult listeners had to discriminate the temporal order of 2,200 and 2,400 Hz target tones presented alone,…

  13. Sequence-selective targeting of duplex DNA by peptide nucleic acids

    DEFF Research Database (Denmark)

    Nielsen, Peter E

    2010-01-01

    Sequence-selective gene targeting constitutes an attractive drug-discovery approach for genetic therapy, with the aim of reducing or enhancing the activity of specific genes at the transcriptional level, or as part of a methodology for targeted gene repair. The pseudopeptide DNA mimic peptide...

  14. The control of attentional target selection in a colour/colour conjunction task.

    Science.gov (United States)

    Berggren, Nick; Eimer, Martin

    2016-11-01

    To investigate the time course of attentional object selection processes in visual search tasks where targets are defined by a combination of features from the same dimension, we measured the N2pc component as an electrophysiological marker of attentional object selection during colour/colour conjunction search. In Experiment 1, participants searched for targets defined by a combination of two colours, while ignoring distractor objects that matched only one of these colours. Reliable N2pc components were triggered by targets and also by partially matching distractors, even when these distractors were accompanied by a target in the same display. The target N2pc was initially equal in size to the sum of the two N2pc components to the two different types of partially matching distractors and became superadditive from approximately 250 ms after search display onset. Experiment 2 demonstrated that the superadditivity of the target N2pc was not due to a selective disengagement of attention from task-irrelevant partially matching distractors. These results indicate that attention was initially deployed separately and in parallel to all target-matching colours, before attentional allocation processes became sensitive to the presence of both matching colours within the same object. They suggest that attention can be controlled simultaneously and independently by multiple features from the same dimension and that feature-guided attentional selection processes operate in parallel for different target-matching objects in the visual field.

  15. Priming of pop-out modulates attentional target selection in visual search: Behavioural and electrophysiological evidence

    OpenAIRE

    Eimer, Martin; Kiss, Monika; Cheung, Theodore

    2009-01-01

    Previous behavioural studies have shown that the repetition of target or distractor features across trials speeds pop-out visual search. We obtained behavioural and event-related brain potential (ERP) measures in two experiments where participants searched for a colour singleton target among homogeneously coloured distractors. An ERP marker of spatially selective attention (N2pc component) was delayed when either target or distractor colours were swapped across successive trials, demonstratin...

  16. Using the Properties of Broad Absorption Line Quasars to Illuminate Quasar Structure

    Science.gov (United States)

    Yong, Suk Yee; King, Anthea L.; Webster, Rachel L.; Bate, Nicholas F.; O'Dowd, Matthew J.; Labrie, Kathleen

    2018-06-01

    A key to understanding quasar unification paradigms is the emission properties of broad absorption line quasars (BALQs). The fact that only a small fraction of quasar spectra exhibit deep absorption troughs blueward of the broad permitted emission lines provides a crucial clue to the structure of quasar emitting regions. To learn whether it is possible to discriminate between the BALQ and non-BALQ populations given the observed spectral properties of a quasar, we employ two approaches: one based on statistical methods and the other supervised machine learning classification, applied to quasar samples from the Sloan Digital Sky Survey. The features explored include continuum and emission line properties, in particular the absolute magnitude, redshift, spectral index, line width, asymmetry, strength, and relative velocity offsets of high-ionisation C IV λ1549 and low-ionisation Mg II λ2798 lines. We consider a complete population of quasars, and assume that the statistical distributions of properties represent all angles where the quasar is viewed without obscuration. The distributions of the BALQ and non-BALQ sample properties show few significant differences. None of the observed continuum and emission line features are capable of differentiating between the two samples. Most published narrow disk-wind models are inconsistent with these observations, and an alternative disk-wind model is proposed. The key feature of the proposed model is a disk-wind filling a wide opening angle with multiple radial streams of dense clumps.

  17. Robust Ground Target Detection by SAR and IR Sensor Fusion Using Adaboost-Based Feature Selection

    Directory of Open Access Journals (Sweden)

    Sungho Kim

    2016-07-01

    Full Text Available Long-range ground targets are difficult to detect in a noisy cluttered environment using either synthetic aperture radar (SAR images or infrared (IR images. SAR-based detectors can provide a high detection rate with a high false alarm rate to background scatter noise. IR-based approaches can detect hot targets but are affected strongly by the weather conditions. This paper proposes a novel target detection method by decision-level SAR and IR fusion using an Adaboost-based machine learning scheme to achieve a high detection rate and low false alarm rate. The proposed method consists of individual detection, registration, and fusion architecture. This paper presents a single framework of a SAR and IR target detection method using modified Boolean map visual theory (modBMVT and feature-selection based fusion. Previous methods applied different algorithms to detect SAR and IR targets because of the different physical image characteristics. One method that is optimized for IR target detection produces unsuccessful results in SAR target detection. This study examined the image characteristics and proposed a unified SAR and IR target detection method by inserting a median local average filter (MLAF, pre-filter and an asymmetric morphological closing filter (AMCF, post-filter into the BMVT. The original BMVT was optimized to detect small infrared targets. The proposed modBMVT can remove the thermal and scatter noise by the MLAF and detect extended targets by attaching the AMCF after the BMVT. Heterogeneous SAR and IR images were registered automatically using the proposed RANdom SAmple Region Consensus (RANSARC-based homography optimization after a brute-force correspondence search using the detected target centers and regions. The final targets were detected by feature-selection based sensor fusion using Adaboost. The proposed method showed good SAR and IR target detection performance through feature selection-based decision fusion on a synthetic

  18. Robust Ground Target Detection by SAR and IR Sensor Fusion Using Adaboost-Based Feature Selection

    Science.gov (United States)

    Kim, Sungho; Song, Woo-Jin; Kim, So-Hyun

    2016-01-01

    Long-range ground targets are difficult to detect in a noisy cluttered environment using either synthetic aperture radar (SAR) images or infrared (IR) images. SAR-based detectors can provide a high detection rate with a high false alarm rate to background scatter noise. IR-based approaches can detect hot targets but are affected strongly by the weather conditions. This paper proposes a novel target detection method by decision-level SAR and IR fusion using an Adaboost-based machine learning scheme to achieve a high detection rate and low false alarm rate. The proposed method consists of individual detection, registration, and fusion architecture. This paper presents a single framework of a SAR and IR target detection method using modified Boolean map visual theory (modBMVT) and feature-selection based fusion. Previous methods applied different algorithms to detect SAR and IR targets because of the different physical image characteristics. One method that is optimized for IR target detection produces unsuccessful results in SAR target detection. This study examined the image characteristics and proposed a unified SAR and IR target detection method by inserting a median local average filter (MLAF, pre-filter) and an asymmetric morphological closing filter (AMCF, post-filter) into the BMVT. The original BMVT was optimized to detect small infrared targets. The proposed modBMVT can remove the thermal and scatter noise by the MLAF and detect extended targets by attaching the AMCF after the BMVT. Heterogeneous SAR and IR images were registered automatically using the proposed RANdom SAmple Region Consensus (RANSARC)-based homography optimization after a brute-force correspondence search using the detected target centers and regions. The final targets were detected by feature-selection based sensor fusion using Adaboost. The proposed method showed good SAR and IR target detection performance through feature selection-based decision fusion on a synthetic database generated

  19. Quasar energy distributions. I. Soft X-ray spectra of quasars

    International Nuclear Information System (INIS)

    Wilkes, B.J.; Elvis, M.

    1987-01-01

    As the initial stage of a study of quasar energy distributions (QEDs), Einstein IPC spectra of 24 quasars are presented. These are combined with previously reported IPC spectra to form a sample of 33 quasars with well-determined soft X-ray slopes. A correlation analysis shows that radio loudness, rather than redshift or luminosity, is fundamentally related to the X-ray slope. This correlation is not followed by higher energy spectra of active galaxies. Two components are required to explain both sets of results. The best-fit column densities are systematically smaller than the Galactic values. The same effect is not present in a sample of BL Lac objects, implying that the effect is intrinsic to the quasars and is caused by a low-energy turnup in the quasar spectra. 74 references

  20. Selection of targets and ion sources for RIB generation at the Holifield Radioactive Ion Beam Facility

    International Nuclear Information System (INIS)

    Alton, G.D.

    1995-01-01

    In this report, the authors describe the performance characteristics for a selected number of target ion sources that will be employed for initial use at the Holifield Radioactive Ion Beam Facility (HRIBF) as well as prototype ion sources that show promise for future use for RIB applications. A brief review of present efforts to select target materials and to design composite target matrix/heat-sink systems that simultaneously incorporate the short diffusion lengths, high permeabilities, and controllable temperatures required to effect fast and efficient diffusion release of the short-lived species is also given

  1. Predictive distractor context facilitates attentional selection of high, but not intermediate and low, salience targets.

    Science.gov (United States)

    Töllner, Thomas; Conci, Markus; Müller, Hermann J

    2015-03-01

    It is well established that we can focally attend to a specific region in visual space without shifting our eyes, so as to extract action-relevant sensory information from covertly attended locations. The underlying mechanisms that determine how fast we engage our attentional spotlight in visual-search scenarios, however, remain controversial. One dominant view advocated by perceptual decision-making models holds that the times taken for focal-attentional selection are mediated by an internal template that biases perceptual coding and selection decisions exclusively through target-defining feature coding. This notion directly predicts that search times remain unaffected whether or not participants can anticipate the upcoming distractor context. Here we tested this hypothesis by employing an illusory-figure localization task that required participants to search for an invariant target amongst a variable distractor context, which gradually changed--either randomly or predictably--as a function of distractor-target similarity. We observed a graded decrease in internal focal-attentional selection times--correlated with external behavioral latencies--for distractor contexts of higher relative to lower similarity to the target. Critically, for low but not intermediate and high distractor-target similarity, these context-driven effects were cortically and behaviorally amplified when participants could reliably predict the type of distractors. This interactive pattern demonstrates that search guidance signals can integrate information about distractor, in addition to target, identities to optimize distractor-target competition for focal-attentional selection. © 2014 Wiley Periodicals, Inc.

  2. INFRARED SPECTRA AND PHOTOMETRY OF COMPLETE SAMPLES OF PALOMAR-GREEN AND TWO MICRON ALL SKY SURVEY QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yong [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Rieke, G. H.; Su, K. Y. L. [Department of Astronomy And Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Ogle, P. M. [Infrared Processing and Analysis Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Balog, Z., E-mail: yshipku@gmail.com [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)

    2014-10-01

    As a step toward a comprehensive overview of the infrared (IR) diagnostics of the central engines and host galaxies of quasars at low redshift, we present Spitzer Space Telescope spectroscopic (5-40 μm) and photometric (24, 70, and 160 μm) measurements of all Palomar-Green (PG) quasars at z < 0.5 and Two Micron All Sky Survey (2MASS) quasars at z < 0.3. We supplement these data with Herschel measurements at 160 μm. The sample is composed of 87 optically selected PG quasars and 52 near-IR-selected 2MASS quasars. Here we present the data, measure the prominent spectral features, and separate emission due to star formation from that emitted by the dusty circumnuclear torus. We find that the mid-IR (5-30 μm) spectral shape for the torus is largely independent of quasar IR luminosity with scatter in the spectral energy distribution (SED) shape of ≲0.2 dex. Except for the silicate features, no large difference is observed between PG (unobscured—silicate emission) and 2MASS (obscured—silicate absorption) quasars. Only mild silicate features are observed in both cases. When in emission, the peak wavelength of the silicate feature tends to be longer than 9.7 μm, possibly indicating effects on grain properties near the active galactic nucleus. The IR color is shown to correlate with the equivalent width of the aromatic features, indicating that the slope of the quasar mid- to far-IR SED is to first order driven by the fraction of radiation from star formation in the IR bands.

  3. Directional enhancement of selected high-order-harmonics from intense laser irradiated blazed grating targets.

    Science.gov (United States)

    Zhang, Guobo; Chen, Min; Liu, Feng; Yuan, Xiaohui; Weng, Suming; Zheng, Jun; Ma, Yanyun; Shao, Fuqiu; Sheng, Zhengming; Zhang, Jie

    2017-10-02

    Relativistically intense laser solid target interaction has been proved to be a promising way to generate high-order harmonics, which can be used to diagnose ultrafast phenomena. However, their emission direction and spectra still lack tunability. Based upon two-dimensional particle-in-cell simulations, we show that directional enhancement of selected high-order-harmonics can be realized using blazed grating targets. Such targets can select harmonics with frequencies being integer times of the grating frequency. Meanwhile, the radiation intensity and emission area of the harmonics are increased. The emission direction is controlled by tailoring the local blazed structure. Theoretical and electron dynamics analysis for harmonics generation, selection and directional enhancement from the interaction between multi-cycle laser and grating target are carried out. These studies will benefit the generation and application of laser plasma-based high order harmonics.

  4. A POPULATION OF X-RAY WEAK QUASARS: PHL 1811 ANALOGS AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    Wu Jianfeng; Brandt, W. N.; Schneider, Donald P.; Hall, Patrick B.; Gibson, Robert R.; Schmidt, Sarah J.; Richards, Gordon T.; Shemmer, Ohad; Just, Dennis W.

    2011-01-01

    We report the results from Chandra and XMM-Newton observations of a sample of 10 type 1 quasars selected to have unusual UV emission-line properties (weak and blueshifted high-ionization lines; strong UV Fe emission) similar to those of PHL 1811, a confirmed intrinsically X-ray weak quasar. These quasars were identified by the Sloan Digital Sky Survey at high redshift (z ∼ 2.2); eight are radio quiet while two are radio intermediate. All of the radio-quiet PHL 1811 analogs, without exception, are notably X-ray weak by a mean factor of ∼13. These sources lack broad absorption lines and have blue UV/optical continua, supporting the hypothesis that they are intrinsically X-ray weak like PHL 1811 itself. However, their average X-ray spectrum appears to be harder than those of typical quasars, which may indicate the presence of heavy intrinsic X-ray absorption. Our sample of radio-quiet PHL 1811 analogs supports a connection between an X-ray weak spectral energy distribution and PHL 1811-like UV emission lines; this connection provides an economical way to identify X-ray weak type 1 quasars. The fraction of radio-quiet PHL 1811 analogs in the radio-quiet quasar population is estimated to be ∼< 1.2%. We have investigated correlations between relative X-ray brightness and UV emission-line properties (e.g., C IV equivalent width and blueshift) for a sample combining our radio-quiet PHL 1811 analogs, PHL 1811 itself, and typical type 1 quasars. These correlation analyses suggest that PHL 1811 analogs may have extreme wind-dominated broad emission-line regions. Observationally, the radio-quiet PHL 1811 analogs appear to be a subset (∼30%) of radio-quiet weak-line quasars (WLQs). The existence of a subset of quasars in which high-ionization 'shielding gas' covers most of the broad emission-line region (BELR), but little more than the BELR, could potentially unify the PHL 1811 analogs and WLQs. The two radio-intermediate PHL 1811 analogs are X-ray bright. X

  5. Purification-Free, Target-Selective Immobilization of a Protein from Cell Lysates.

    Science.gov (United States)

    Cha, Jaehyun; Kwon, Inchan

    2018-02-27

    Protein immobilization has been widely used for laboratory experiments and industrial processes. Preparation of a recombinant protein for immobilization usually requires laborious and expensive purification steps. Here, a novel purification-free, target-selective immobilization technique of a protein from cell lysates is reported. Purification steps are skipped by immobilizing a target protein containing a clickable non-natural amino acid (p-azidophenylalanine) in cell lysates onto alkyne-functionalized solid supports via bioorthogonal azide-alkyne cycloaddition. In order to achieve a target protein-selective immobilization, p-azidophenylalanine was introduced into an exogenous target protein, but not into endogenous non-target proteins using host cells with amber codon-free genomic DNAs. Immobilization of superfolder fluorescent protein (sfGFP) from cell lysates is as efficient as that of the purified sfGFP. Using two fluorescent proteins (sfGFP and mCherry), the authors also demonstrated that the target proteins are immobilized with a minimal immobilization of non-target proteins (target-selective immobilization). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Altering spatial priority maps via statistical learning of target selection and distractor filtering.

    Science.gov (United States)

    Ferrante, Oscar; Patacca, Alessia; Di Caro, Valeria; Della Libera, Chiara; Santandrea, Elisa; Chelazzi, Leonardo

    2018-05-01

    The cognitive system has the capacity to learn and make use of environmental regularities - known as statistical learning (SL), including for the implicit guidance of attention. For instance, it is known that attentional selection is biased according to the spatial probability of targets; similarly, changes in distractor filtering can be triggered by the unequal spatial distribution of distractors. Open questions remain regarding the cognitive/neuronal mechanisms underlying SL of target selection and distractor filtering. Crucially, it is unclear whether the two processes rely on shared neuronal machinery, with unavoidable cross-talk, or they are fully independent, an issue that we directly addressed here. In a series of visual search experiments, participants had to discriminate a target stimulus, while ignoring a task-irrelevant salient distractor (when present). We systematically manipulated spatial probabilities of either one or the other stimulus, or both. We then measured performance to evaluate the direct effects of the applied contingent probability distribution (e.g., effects on target selection of the spatial imbalance in target occurrence across locations) as well as its indirect or "transfer" effects (e.g., effects of the same spatial imbalance on distractor filtering across locations). By this approach, we confirmed that SL of both target and distractor location implicitly bias attention. Most importantly, we described substantial indirect effects, with the unequal spatial probability of the target affecting filtering efficiency and, vice versa, the unequal spatial probability of the distractor affecting target selection efficiency across locations. The observed cross-talk demonstrates that SL of target selection and distractor filtering are instantiated via (at least partly) shared neuronal machinery, as further corroborated by strong correlations between direct and indirect effects at the level of individual participants. Our findings are compatible

  7. Discovery of a bright quasar without a massive host galaxy.

    Science.gov (United States)

    Magain, Pierre; Letawe, Géraldine; Courbin, Frédéric; Jablonka, Pascale; Jahnke, Knud; Meylan, Georges; Wisotzki, Lutz

    2005-09-15

    A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy. Because the optical luminosity of quasars exceeds that of their host galaxy, disentangling the two components can be difficult. This led in the 1990s to the controversial claim of the discovery of 'naked' quasars. Since then, the connection between quasars and galaxies has been well established. Here we report the discovery of a quasar lying at the edge of a gas cloud, whose size is comparable to that of a small galaxy, but whose spectrum shows no evidence for stars. The gas in the cloud is excited by the quasar itself. If a host galaxy is present, it is at least six times fainter than would normally be expected for such a bright quasar. The quasar is interacting dynamically with a neighbouring galaxy, whose gas might be feeding the black hole.

  8. Spatial distribution, luminosity function and cosmological evolution of quasars

    International Nuclear Information System (INIS)

    Mathez, G.

    1981-01-01

    The different ways of studying quasars statistics and evolution are reviewed. Attempt is given to deduce, from the observed evolution, some constraints on physical models of energy sources in quasars [fr

  9. High-redshift quasars in the Cold Dark Matter cosmogony

    International Nuclear Information System (INIS)

    Efstathiou, G.; Rees, M.J.

    1988-01-01

    The relationship between high-redshift quasars and the epoch of galaxy formation in the Cold Dark Matter (CDM) cosmogony is investigated. Luminous quasars could only form after galactic sized systems had collapsed. A constant comoving density of luminous quasars between z = 2 and z = 4 is compatible with the CDM model if quasars are short-lived and radiate at about the Eddington limit. However, according to the CDM model the abundance of high-luminosity quasars must decline exponentially at higher redshifts. Even if all protogalaxies form quasars, and about 1 per cent of the baryons within a protogalaxy collapse into a compact object, a steep fall in the density of quasars with L > 10 47 erg s -1 at redshifts z ≥ 5. The existence of a 'cut-off' in the quasar numbers at high redshift could therefore supply an important test of the CDM theory. (author)

  10. Molecular Connectivity Predefines Polypharmacology: Aliphatic Rings, Chirality, and sp3 Centers Enhance Target Selectivity

    Directory of Open Access Journals (Sweden)

    Stefania Monteleone

    2017-08-01

    Full Text Available Dark chemical matter compounds are small molecules that have been recently identified as highly potent and selective hits. For this reason, they constitute a promising class of possible candidates in the process of drug discovery and raise the interest of the scientific community. To this purpose, Wassermann et al. (2015 have described the application of 2D descriptors to characterize dark chemical matter. However, their definition was based on the number of reported positive assays rather than the number of known targets. As there might be multiple assays for one single target, the number of assays does not fully describe target selectivity. Here, we propose an alternative classification of active molecules that is based on the number of known targets. We cluster molecules in four classes: black, gray, and white compounds are active on one, two to four, and more than four targets respectively, whilst inactive compounds are found to be inactive in the considered assays. In this study, black and inactive compounds are found to have not only higher solubility, but also a higher number of chiral centers, sp3 carbon atoms and aliphatic rings. On the contrary, white compounds contain a higher number of double bonds and fused aromatic rings. Therefore, the design of a screening compound library should consider these molecular properties in order to achieve target selectivity or polypharmacology. Furthermore, analysis of four main target classes (GPCRs, kinases, proteases, and ion channels shows that GPCR ligands are more selective than the other classes, as the number of black compounds is higher in this target superfamily. On the other side, ligands that hit kinases, proteases, and ion channels bind to GPCRs more likely than to other target classes. Consequently, depending on the target protein family, appropriate screening libraries can be designed in order to minimize the likelihood of unwanted side effects early in the drug discovery process

  11. The Clustering of High-redshift (2.9 ≤ z ≤ 5.1) Quasars in SDSS Stripe 82

    Science.gov (United States)

    Timlin, John D.; Ross, Nicholas P.; Richards, Gordon T.; Myers, Adam D.; Pellegrino, Andrew; Bauer, Franz E.; Lacy, Mark; Schneider, Donald P.; Wollack, Edward J.; Zakamska, Nadia L.

    2018-05-01

    We present a measurement of the two-point autocorrelation function of photometrically selected high-z quasars over ∼100 deg2 on the Sloan Digital Sky Survey Stripe 82 field. Selection is performed using three machine-learning algorithms in a six-dimensional optical/mid-infrared color space. Optical data from the Sloan Digital Sky Survey are combined with overlapping deep mid-infrared data from the Spitzer IRAC Equatorial Survey and the Spitzer-HETDEX Exploratory Large-Area survey. Our selection algorithms are trained on the colors of known high-z quasars. The selected quasar sample consists of 1378 objects and contains both spectroscopically confirmed quasars and photometrically selected quasar candidates. These objects span a redshift range of 2.9 ≤ z ≤ 5.1 and are generally fainter than i = 20.2, a regime that has lacked sufficient number density to perform autocorrelation function measurements of photometrically classified quasars. We compute the angular correlation function of these data, marginally detecting quasar clustering. We fit a single power law with an index of δ = 1.39 ± 0.618 and amplitude of θ 0 = 0.‧71 ± 0.‧546 . A dark matter model is fit to the angular correlation function to estimate the linear bias. At the average redshift of our survey ( =3.38), the bias is b = 6.78 ± 1.79. Using this bias, we calculate a characteristic dark matter halo mass of 1.70–9.83× {10}12{h}-1 {M}ȯ . Our bias estimate suggests that quasar feedback intermittently shuts down the accretion of gas onto the central supermassive black hole at early times. If confirmed, these results hint at a level of luminosity dependence in the clustering of quasars at high-z.

  12. Discovery of three strongly lensed quasars in the Sloan Digital Sky Survey

    Science.gov (United States)

    Williams, P. R.; Agnello, A.; Treu, T.; Abramson, L. E.; Anguita, T.; Apostolovski, Y.; Chen, G. C.-F.; Fassnacht, C. D.; Hsueh, J. W.; Lemaux, B. C.; Motta, V.; Oldham, L.; Rojas, K.; Rusu, C. E.; Shajib, A. J.; Wang, X.

    2018-06-01

    We present the discovery of three quasar lenses in the Sloan Digital Sky Survey, selected using two novel photometry-based selection techniques. The J0941+0518 system, with two point sources separated by 5.46 arcsec on either side of a galaxy, has source and lens redshifts 1.54 and 0.343. Images of J2257+2349 show two point sources separated by 1.67 arcsec on either side of an E/S0 galaxy. The extracted spectra show two images of the same quasar at zs = 2.10. SDSS J1640+1045 has two quasar spectra at zs = 1.70 and fits to the SDSS and Pan-STARRS images confirm the presence of a galaxy between the two point sources. We observed 56 photometrically selected lens candidates in this follow-up campaign, confirming three new lenses, re-discovering one known lens, and ruling out 36 candidates, with 16 still inconclusive. This initial campaign demonstrates the power of purely photometric selection techniques in finding lensed quasars.

  13. A QUASAR CATALOG WITH SIMULTANEOUS UV, OPTICAL, AND X-RAY OBSERVATIONS BY SWIFT

    International Nuclear Information System (INIS)

    Wu Jian; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P.; Gronwall, Caryl; Porterfield, Blair L.; Vanden Berk, Daniel; Wesolowski, Sarah

    2012-01-01

    We have compiled a catalog of optically selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma-ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both Ultraviolet Optical Telescope (UVOT) and X-Ray Telescope (XRT) observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ∼60% which rises to ∼85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution (SED) for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about ∼0.3 dex to the quasar luminosity. We re-visit the α ox -L 2500Å relation by selecting a clean sample with only Type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared with studies that use non-simultaneous UV/optical and X-ray data. We only found a weak correlation between L bol /L Edd and α UV . We do not find significant correlations between α x and α ox , α ox and α UV , and α x and log L(0.3-10 keV). The correlations between α UV and α x , α ox and α x , α ox and α UV , L bol /L Edd and α x , and L bol /L Edd and α ox are stronger among low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state.

  14. The kinetically dominated quasar 3C 418

    Science.gov (United States)

    Punsly, Brian; Kharb, Preeti

    2017-06-01

    The existence of quasars that are kinetically dominated, where the jet kinetic luminosity, Q, is larger than the total (infrared to X-ray) thermal luminosity of the accretion flow, Lbol, provides a strong constraint on the fundamental physics of relativistic jet formation. Since quasars have high values of Lbol by definition, only ˜10 kinetically dominated quasars (with \\overline{Q}/L_{bol}>1) have been found, where \\overline{Q} is the long-term time-averaged jet power. We use low-frequency (151 MHz-1.66 GHz) observations of the quasar 3C 418 to determine \\overline{Q}≈ 5.5 ± 1.3 × 10^{46} {erg s^{-1}}. Analysis of the rest-frame ultraviolet spectrum indicates that this equates to 0.57 ± 0.28 times the Eddington luminosity of the central supermassive black hole and \\overline{Q}/L_{bol} ≈ 4.8 ± 3.1, making 3C 418 one of the most kinetically dominated quasars found to date. It is shown that this maximal \\overline{Q}/L_{bol} is consistent with models of magnetically arrested accretion of jet production in which the jet production reproduces the observed trend of a decrement in the extreme ultraviolet continuum as the jet power increases. This maximal condition corresponds to an almost complete saturation of the inner accretion flow with vertical large-scale magnetic flux (maximum saturation).

  15. Highly Accreting Quasars at High Redshift

    Directory of Open Access Journals (Sweden)

    Mary L. Martínez-Aldama

    2018-01-01

    Full Text Available We present preliminary results of a spectroscopic analysis for a sample of type 1 highly accreting quasars (L/LEdd ~ 1.0 at high redshift, z ~2–3. The quasars were observed with the OSIRIS spectrograph on the GTC 10.4 m telescope located at the Observatorio del Roque de los Muchachos in La Palma. The highly accreting quasars were identified using the 4D Eigenvector 1 formalism, which is able to organize type 1 quasars over a broad range of redshift and luminosity. The kinematic and physical properties of the broad line region have been derived by fitting the profiles of strong UV emission lines such as Aliiiλ1860, Siiii]λ1892 and Ciii]λ1909. The majority of our sources show strong blueshifts in the high-ionization lines and high Eddington ratios which are related with the productions of outflows. The importance of highly accreting quasars goes beyond a detailed understanding of their physics: their extreme Eddington ratio makes them candidates standard candles for cosmological studies.

  16. Highly Accreting Quasars at High Redshift

    Science.gov (United States)

    Martínez-Aldama, Mary L.; Del Olmo, Ascensión; Marziani, Paola; Sulentic, Jack W.; Negrete, C. Alenka; Dultzin, Deborah; Perea, Jaime; D'Onofrio, Mauro

    2017-12-01

    We present preliminary results of a spectroscopic analysis for a sample of type 1 highly accreting quasars (LLedd>0.2) at high redshift, z 2-3. The quasars were observed with the OSIRIS spectrograph on the GTC 10.4 m telescope located at the Observatorio del Roque de los Muchachos in La Palma. The highly accreting quasars were identified using the 4D Eigenvector 1 formalism, which is able to organize type 1 quasars over a broad range of redshift and luminosity. The kinematic and physical properties of the broad line region have been derived by fitting the profiles of strong UV emission lines such as AlIII, SiIII and CIII. The majority of our sources show strong blueshifts in the high-ionization lines and high Eddington ratios which are related with the productions of outflows. The importance of highly accreting quasars goes beyond a detailed understanding of their physics: their extreme Eddington ratio makes them candidates standard candles for cosmological studies.

  17. Spectroscopy of the fuzz associated with four quasars

    International Nuclear Information System (INIS)

    Balick, B.; Heckman, T.M.

    1983-01-01

    The spectroscopic properties of the ''fuzz'' near four quasars are consistent with starlight in a galactic environment at essentially the same redshift as the quasar. Apparently, then, the same processes that determine the redshifts of galaxies also determine the redshifts of quasars

  18. Occurrence Prospect of HDR and Target Site Selection Study in Southeastern of China

    Science.gov (United States)

    Lin, W.; Gan, H.

    2017-12-01

    Hot dry rock (HDR) geothermal resource is one of the most important clean energy in future. Site selection a HDR resource is a fundamental work to explore the HDR resources. This paper compiled all the HDR development projects domestic and abroad, and summarized the location of HDR geothermal geological index. After comparing the geological background of HDR in the southeast coastal area of China, Yangjiang Xinzhou in Guangdong province, Leizhou Peninsula area, Lingshui in Hainan province and Huangshadong in Guangzhou were selected from some key potential target area along the southeast coast of China. Deep geothermal field model of the study area is established based on the comprehensive analysis of the target area of deep geothermal geological background and deep thermal anomalies. This paper also compared the hot dry rock resources target locations, and proposed suggestions for the priority exploration target area and exploration scheme.

  19. Selection of IFE target materials from a safety and environmental perspective

    Energy Technology Data Exchange (ETDEWEB)

    Latkowski, J.F. E-mail: latkowski1@llnl.gov; Sanz, J.; Reyes, S.; Gomez del Rio, J

    2001-05-21

    Target materials for inertial fusion energy (IFE) power plant designs might be selected for a wide variety of reasons including wall absorption of driver energy, material opacity, cost and ease of fabrication. While each of these issues are of great importance, target materials should also be selected based upon their safety and environmental (S and E) characteristics. The present work focuses on the recycling, waste management and accident dose characteristics of potential target materials. If target materials are recycled so that the quantity is small, isotopic separation may be economically viable. Therefore, calculations have been completed for all stable isotopes for all elements from lithium to polonium. The results of these calculations are used to identify specific isotopes and elements that are most likely to be offensive as well as those most likely to be acceptable in terms of their S and E characteristics.

  20. Selection of IFE target materials from a safety and environmental perspective

    Science.gov (United States)

    Latkowski, J. F.; Sanz, J.; Reyes, S.; Gomez del Rio, J.

    2001-05-01

    Target materials for inertial fusion energy (IFE) power plant designs might be selected for a wide variety of reasons including wall absorption of driver energy, material opacity, cost and ease of fabrication. While each of these issues are of great importance, target materials should also be selected based upon their safety and environmental (S&E) characteristics. The present work focuses on the recycling, waste management and accident dose characteristics of potential target materials. If target materials are recycled so that the quantity is small, isotopic separation may be economically viable. Therefore, calculations have been completed for all stable isotopes for all elements from lithium to polonium. The results of these calculations are used to identify specific isotopes and elements that are most likely to be offensive as well as those most likely to be acceptable in terms of their S&E characteristics.

  1. The spatially global control of attentional target selection in visual search

    OpenAIRE

    Berggren, Nick; Jenkins, M.; McCants, C.W.; Eimer, Martin

    2017-01-01

    Glyn Humphreys and his co-workers have made numerous important theoretical and empirical contributions to research on visual search. They have introduced the concept of attentional target templates and investigated the nature of these templates and how they are involved in the control of search performance. In the experiments reported here, we investigated whether feature-specific search template for particular colours can guide target selection independently for different regions of visual s...

  2. Impact of high-risk conjunctions on Active Debris Removal target selection

    OpenAIRE

    Lidtke, Aleksander A.; Lewis, Hugh G.; Armellin, Roberto

    2015-01-01

    All rights reserved.Space debris simulations show that if current space launches continue unchanged, spacecraft operations might become difficult in the congested space environment. It has been suggested that Active Debris Removal (ADR) might be necessary in order to prevent such a situation. Selection of objects to be targeted by ADR is considered important because removal of non-relevant objects will unnecessarily increase the cost of ADR. One of the factors to be used in this ADR target se...

  3. Black-hole masses of distant quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2011-01-01

    A brief overview of the methods commonly used to determine or estimate the black hole mass in quiescent or active galaxies is presented and it is argued that the use of mass-scaling relations is both a reliable and the preferred method to apply to large samples of distant quasars. The method uses...... that the black hole masses are very large, of order 1 to 10 billion solar masses, even at the highest redshifts of 4 to 6. The black holes must build up their mass very fast in the early universe. Yet they do not grow much larger than that: a maximum mass of about 10 billion solar masses is also observed....... Preliminary mass functions of active black holes are presented for several quasar samples, including the Sloan Digital Sky Survey. Finally, common concerns related to the application of the mass scaling relations, especially for high redshift quasars, are briefly discussed....

  4. Probing Extragalactic Planets Using Quasar Microlensing

    Science.gov (United States)

    Dai, Xinyu; Guerras, Eduardo

    2018-02-01

    Previously, planets have been detected only in the Milky Way galaxy. Here, we show that quasar microlensing provides a means to probe extragalactic planets in the lens galaxy, by studying the microlensing properties of emission close to the event horizon of the supermassive black hole of the background quasar, using the current generation telescopes. We show that a population of unbound planets between stars with masses ranging from Moon to Jupiter masses is needed to explain the frequent Fe Kα line energy shifts observed in the gravitationally lensed quasar RXJ 1131–1231 at a lens redshift of z = 0.295 or 3.8 billion lt-yr away. We constrain the planet mass-fraction to be larger than 0.0001 of the halo mass, which is equivalent to 2000 objects ranging from Moon to Jupiter mass per main-sequence star.

  5. Doppler interpretation of quasar red shifts.

    Science.gov (United States)

    Zapolsky, H S

    1966-08-05

    The hypothesis that the quasistellar sources (quasars) are local objects moving with velocities close to the speed of light is examined. Provided there is no observational cutoff on apparent bolometric magnitude for the quasars, the transverse Doppler effect leads to the expectation of fewer blue shifts than red shifts for an isotropic distribution of velocities. Such a distribution also yields a function N(z), the number of objects with red shift less than z which is not inconsistent with the present data. On the basis of two extreme assumptions concerning the origin of such rapidly moving sources, we computed curves of red shift plotted against magnitude. In particular, the curve obtained on the assumption that the quasars originated from an explosion in or nearby our own galaxy is in as good agreement with the observations as the curve of cosmological red shift plotted against magnitude.

  6. Quasars, companion galaxies and Poisson statistics

    International Nuclear Information System (INIS)

    Webster, A.

    1982-01-01

    Arp has presented a sample of quasars lying close to the companion galaxies of bright spirals, from which he estimates a value of 10 -17 for the probability that the galaxies and quasars are sited independently on the celestial sphere; Browne, however, has found a simple fallacy in the statistics which accounts for about 10 of the 17 orders of magnitude. Here we draw attention to an obscure part of Arp's calculation which we have been unable to repeat; if it is carried out in what seems to be the most straightforward way, about five more orders may be accounted for. In consequence, it is not clear that the sample contains any evidence damaging to the popular notion that the redshifts of quasars indicate distance through the Hubble Law. (author)

  7. Contextual control over selective attention: evidence from a two-target method.

    Science.gov (United States)

    MacLellan, Ellen; Shore, David I; Milliken, Bruce

    2015-07-01

    Selective attention is generally studied with conflict tasks, using response time as the dependent measure. Here, we study the impact of selective attention to a first target, T1, presented simultaneously with a distractor, on the accuracy of subsequent encoding of a second target item, T2. This procedure produces an "attentional blink" (AB) effect much like that reported in other studies, and allowed us to study the influence of context on cognitive control with a novel method. In particular, we examined whether preparation to attend selectively to T1 had an impact on the selective encoding of T1 that would translate to report of T2. Preparation to attend selectively was manipulated by varying whether difficult selective attention T1 trials were presented in the context of other difficult selective attention T1 trials. The results revealed strong context effects of this nature, with smaller AB effects when difficult selective attention T1 trials were embedded in a context with many, rather than few, other difficult selective attention T1 trials. Further, the results suggest that both the trial-to-trial local context and the block-wide global context modulate performance in this task.

  8. A Hungry Quasar Caught in the Act

    Science.gov (United States)

    2001-05-01

    The VLT Secures Spectacular Image of Distant Gravitational Interaction Summary A new image of a distant quasar (the luminous core of an "active" galaxy) shows that it is engaged in a gravitational battle with its neighbouring galaxies . It also provides information on how supermassive black holes present in the center of quasars are fed. Using the FORS2 multi-mode instrument at the ESO 8.2-m VLT KUEYEN telescope on Paranal (Chile), a team of German astronomers [1] obtained a spectacular image of the close and complex environment of the distant quasar "HE 1013-2136", located some 10 billion light-years away [2]. The remarkable structures revealed in this photo lend support to the hypothesis that quasar activity is connected to gravitational interaction between galaxies, already at this early epoch of the Universe (about 5 billion years after the Big Bang). PR Photo 20a/01 : A VLT image of the Quasar HE 1013-2136 . PR Photo 20b/01 : A sharpened version of the same image. Feeding the Black Hole "Quasars" (Quasi-Stellar Objects) were first discovered by Dutch-American astronomer Maarten Schmidt in 1963 as distant, energetic objects of star-like appearance. Since then, more than 15,000 quasars have been found and we now know that they are the luminous cores at the heart of distant galaxies. Such "Active Galactic Nuclei (AGN)" are thought to host Supermassive Black Holes of up to one billion solar masses at their centres. Black Holes represent the densest possible state of matter; if the Earth were to become one, it would measure no more than a few millimetres across. The Black Hole in a galaxy gobbles up the gas and dust of its host, a process that efficiently powers the luminous core that we observe as a point-like "quasar". A Black Hole must be continuously fed to remain active. During an active phase of typically 100 million years, the Black Hole in a quasar swallows material with a total weight of up to 10 solar masses every year. This may be predominantly in the

  9. Social exclusion impairs distractor suppression but not target enhancement in selective attention.

    Science.gov (United States)

    Xu, Mengsi; Li, Zhiai; Diao, Liuting; Fan, Lingxia; Zhang, Lijie; Yuan, Shuge; Yang, Dong

    2017-11-01

    Social exclusion has been thought to weaken one's ability to exert inhibitory control. Existing studies have primarily focused on the relationship between exclusion and behavioral inhibition, and have reported that exclusion impairs behavioral inhibition. However, whether exclusion also affects selective attention, another important aspect of inhibitory control, remains unknown. Therefore, the current study aimed to explore whether social exclusion impairs selective attention, and to specifically examine its effect on two hypothesized mechanisms of selective attention: target enhancement and distractor suppression. The Cyberball game was used to manipulate social exclusion. Participants then performed a visual search task while event-related potentials were recorded. In the visual search task, target and salient distractor were either both presented laterally or one was presented on the vertical midline and the other laterally. Results showed that social exclusion differentially affected target and distractor processing. While exclusion impaired distractor suppression, reflected as smaller distractor-positivity (Pd) amplitudes for the exclusion group compared to the inclusion group, it did not affect target enhancement, reflected as similar target-negativity (Nt) amplitudes for both the exclusion and inclusion groups. Together, these results extend our understanding of the relationship between exclusion and inhibitory control, and suggest that social exclusion affects selective attention in a more complex manner than previously thought. Copyright © 2017. Published by Elsevier B.V.

  10. The Sloan Digital Sky Survey Quasar Catalog. 4. Fifth Data Release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; Hall, Patrick B.; Richards, Gordon T.; Strauss, Michael A.; Vanden Berk, Daniel E.; Anderson, Scott F.; Brandt, W.N.; Fan, Xiao-Hui; Jester,; Gray, Jim; Gunn, James E.; /Penn State U., Astron. Astrophys. /York U., Canada /Johns Hopkins U. /Princeton U. Observ. /Washington U., Seattle, Astron. Dept. /Arizona

    2007-04-01

    We present the fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog contains 77,429 objects; this is an increase of over 30,000 entries since the previous edition. The catalog consists of the objects in the SDSS Fifth Data Release that have luminosities larger than M{sub i} = -22.0 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or have interesting/complex absorption features, are fainter than i {approx} 15.0, and have highly reliable redshifts. The area covered by the catalog is {approx} 5740 deg{sup 2}. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.48; the catalog includes 891 quasars at redshifts greater than four, of which 36 are at redshifts greater than five. Approximately half of the catalog quasars have i < 19; nearly all have i < 21. For each object the catalog presents positions accurate to better than 0.2-minutes rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains basic radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 {angstrom} at a spectral resolution of {approx_equal} 2000; the spectra can be retrieved from the public database using the information provided in the catalog. The average SDSS colors of quasars as a function of redshift, derived from the catalog entries, are presented in tabular form. Approximately 96% of the objects in the catalog were discovered by the SDSS.

  11. Transesophageal color Doppler evaluation of obstructive lesions using the new "Quasar" technology.

    Science.gov (United States)

    Fan, P; Nanda, N C; Gatewood, R P; Cape, E G; Yoganathan, A P

    1995-01-01

    Due to the unavoidable problem of aliasing, color flow signals from high blood flow velocities cannot be measured directly by conventional color Doppler. A new technology termed Quantitative Un-Aliased Speed Algorithm Recognition (Quasar) has been developed to overcome this limitation. Employing this technology, we used transesophageal color Doppler echocardiography to investigate whether the velocities detected by the Quasar would correlate with those obtained by continuous-wave Doppler both in vitro and in vivo. In the in vitro study, a 5.0 MHz transesophageal transducer of a Kontron Sigma 44 color Doppler flow system was used. Fourteen different peak velocities calculated and recorded by color Doppler-guided continuous-wave Doppler were randomly selected. In the clinical study, intraoperative transesophageal echocardiography was performed using the same transducer 18 adults (13 aortic valve stenosis, 2 aortic and 2 mitral stenosis, 2 hypertrophic obstructive cardiomyopathy and 1 mitral valve stenosis). Following each continuous-wave Doppler measurement, the Quasar was activated, and a small Quasar marker was placed in the brightest area of the color flow jet to obtain the maximum mean velocity readout. The maximum mean velocities measured by Quasar closely correlated with maximum peak velocities obtained by color flow guided continuous-wave Doppler in both in vitro (0.53 to 1.65 m/s, r = 0.99) and in vivo studies (1.50 to 6.01 m/s, r = 0.97). We conclude that the new Quasar technology can accurately measure high blood flow velocities during transesophageal color Doppler echocardiography. This technique has the potential of obviating the need for continuous-wave Doppler.

  12. SPITZER OBSERVATIONS OF YOUNG RED QUASARS

    International Nuclear Information System (INIS)

    Urrutia, Tanya; Lacy, Mark; Spoon, Henrik; Glikman, Eilat; Petric, Andreea; Schulz, Bernhard

    2012-01-01

    We present mid-infrared spectra and photometry of 13 redshift 0.4 < z < 1 dust reddened quasars obtained with Spitzer IRS and MIPS. We compare properties derived from their infrared spectral energy distributions (intrinsic active galactic nucleus (AGN) luminosity and far-infrared luminosity from star formation) to the host luminosities and morphologies from Hubble Space Telescope imaging, and black hole masses estimated from optical and/or near-infrared spectroscopy. Our results are broadly consistent with models in which most dust reddened quasars are an intermediate phase between a merger-driven starburst triggering a completely obscured AGN, and a normal, unreddened quasar. We find that many of our objects have high accretion rates, close to the Eddington limit. These objects tend to fall below the black hole mass-bulge luminosity relation as defined by local galaxies, whereas most of our low accretion rate objects are slightly above the local relation, as typical for normal quasars at these redshifts. Our observations are therefore most readily interpreted in a scenario in which galaxy stellar mass growth occurs first by about a factor of three in each merger/starburst event, followed sometime later by black hole growth by a similar amount. We do not, however, see any direct evidence for quasar feedback affecting star formation in our objects, for example, in the form of a relationship between accretion rate and star formation. Five of our objects, however, do show evidence for outflows in the [O III]5007 Å emission line profile, suggesting that the quasar activity is driving thermal winds in at least some members of our sample.

  13. Candidate Targets for New Anti-Virulence Drugs: Selected Cases of Bacterial Adhesion and Biofilm Formation

    DEFF Research Database (Denmark)

    Klemm, Per; Hancock, Viktoria; Kvist, Malin

    2007-01-01

    is particularly problematic in medical contexts because biofilm-associated bacteria are particularly hard to eradicate. Several promising candidate drugs that target bacterial adhesion and biofilm formation are being developed. Some of these might be valuable weapons for fighting infectious diseases in the future...... formation are highly attractive targets for new drugs. Specific adhesion provides bacteria with target selection and prevents removal by hydrodynamic flow forces. Bacterial adhesion is of paramount importance for bacterial pathogenesis. Adhesion is also the first step in biofilm formation. Biofilm formation...

  14. Galaxy correlations at high redshift and the environment of quasars

    International Nuclear Information System (INIS)

    Phillipps, Steven

    1986-01-01

    In close line-of-sight pairs of quasars absorption lines may be seen in the spectrum of the further quasar at a redshift corresponding to that of the nearer quasar. This is indicative of the presence of an intervening galaxy belonging to the same cluster as the (galaxy containing the) nearer quasar. The likelihood of this occurring is calculated in terms of the galaxy correlation function and it is found that present results already suggest that quasars at redshifts above one must be associated with rich clusters. (author)

  15. TARGET MARKET SELECTION IN FRESH FRUIT-VEGETABLE SECTOR USING FUZZY VIKOR METHOD

    OpenAIRE

    Tosun, Nedret

    2017-01-01

    Purpose- Companieshave to open up to new markets in order to develop and increase theircompetitiveness in the face of globalization and technological revolution.Target market selection is an important issue that needs to be addressed withpriority in terms of efficient use of resources. Methodology- The problemof market selection is a multi-criteria decision-making problem due to itsnature which requires the evaluation of different and sometimes conflictingcriteria in the decision-making proce...

  16. A Survey of z>5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z~6

    Science.gov (United States)

    Fan, Xiaohui; Narayanan, Vijay K.; Lupton, Robert H.; Strauss, Michael A.; Knapp, Gillian R.; Becker, Robert H.; White, Richard L.; Pentericci, Laura; Leggett, S. K.; Haiman, Zoltán; Gunn, James E.; Ivezić, Željko; Schneider, Donald P.; Anderson, Scott F.; Brinkmann, J.; Bahcall, Neta A.; Connolly, Andrew J.; Csabai, István; Doi, Mamoru; Fukugita, Masataka; Geballe, Tom; Grebel, Eva K.; Harbeck, Daniel; Hennessy, Gregory; Lamb, Don Q.; Miknaitis, Gajus; Munn, Jeffrey A.; Nichol, Robert; Okamura, Sadanori; Pier, Jeffrey R.; Prada, Francisco; Richards, Gordon T.; Szalay, Alex; York, Donald G.

    2001-12-01

    We present the results from a survey of i-dropout objects selected from ~1550 deg2 of multicolor imaging data from the Sloan Digital Sky Survey to search for luminous quasars at z>~5.8. Objects with i*-z*>2.2 and z*0.90. The ARC 3.5 m spectrum of SDSSp J103027.10+052455.0 shows that over a range of ~300 Å immediately blueward of the Lyα emission, the average transmitted flux is only 0.003+/-0.020 times that of the continuum level, consistent with zero flux over a ~300 Å range of the Lyα forest region and suggesting a tentative detection of the complete Gunn-Peterson trough. The existence of strong metal lines in the quasar spectra suggests early metal enrichment in the quasar environment. The three new objects, together with the previously published z=5.8 quasar SDSSp J104433.04-012502.2, form a complete color-selected flux-limited sample at z>~5.8. We estimate the selection function of this sample, taking into account the estimated variations in the quasar spectral energy distribution, as well as observational photometric errors. We find that at z=6, the comoving density of luminous quasars at M1450Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina) on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, made possible by the generous financial support of the W. M. Keck Foundation; on observations obtained at the German-Spanish Astronomical Centre, Calar Alto Observatory, operated by the Max Planck Institute for Astronomy, Heidelberg, jointly with the Spanish National Commission for Astronomy; and on observations obtained at UKIRT, which is operated by the Joint Astronomy Centre on behalf of the UK Particle Physics and Astronomy Research Council.

  17. Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T.; Hall, Patrick B.; Schneider, Donald P.; Szalay, Alexander S.; Thakar, Anirudda R.; Berk, Daniel E.Vanden; Anderson, Scott F.; Bahcall, Neta A.; /KIPAC, Menlo Park

    2006-11-30

    We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 {le} z {le} 5.4 selected over 4041 deg{sup 2} from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form {zeta}(r) = (r/r{sub 0}){sup -{gamma}}, the fitted parameters in comoving coordinates are r{sub 0} = 15.2 {+-} 2.7 h{sup -1} Mpc and {gamma} = 2.0 {+-} 0.3, over a scale range 4 {le} r{sub p} {le} 150 h{sup -1} Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z {approx} 1.5 counterparts, which have a comoving clustering length r{sub 0} {approx} 6.5 h{sup -1} Mpc. Dividing our sample into two redshift bins: 2.9 {le} z {le} 3.5 and z {ge} 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r{sub 0} = 16.9 {+-} 1.7 h{sup -1} Mpc for the former, and r{sub 0} = 24.3 {+-} 2.4 h{sup -1} Mpc for the latter. Strong clustering at high redshift indicates that quasars are found in very massive, and therefore highly biased, halos. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifetimes and duty cycle. Using the Sheth & Tormen halo mass function, the quasar lifetime is estimated to lie in the range 4 {approx} 50 Myr for quasars with 2.9 {le} z {le} 3.5; and 30 {approx} 600 Myr for quasars with z {ge} 3.5. The corresponding duty cycles are 0.004 {approx} 0.05 for the lower redshift bin and 0.03 {approx} 0.6 for the higher redshift bin. The minimum mass of halos in which these quasars reside is 2-3 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with 2.9 {le} z {le} 3.5 and 4-6 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with z {ge} 3.5; the effective bias factor b{sub eff} increases with redshift, e.g., b

  18. Quasars: Cosmological evolution and x-ray background contribution

    International Nuclear Information System (INIS)

    Schmidt, M.; Green, R.F.

    1986-01-01

    The luminosity function of quasars varies with redshift or cosmic epoch. The authors discuss how the luminosity function and its evolution can be determined from complete samples of quasars. They first concentrate on optical survey of quasars. For quasars of medium luminosity, the co-moving space density rises very steeply with redshift. Quasars of lower luminosity exhibit a slower increase of density with redshift, resulting in luminosity-dependent evolution of the space density. They also discuss evidence for a cutoff of quasar redshift and for a possible dependence of the cutoff on luminosity. They evaluate X-ray counts of quasars and show the need for negative X-ray luminosity evolution in order to explain the counts and the low average redshifts of X-ray quasars. As a consequence, the quasar contribution to the X-ray background is lower than originally suspected. They discuss other extragalactic contributors to the X-ray background and conclude that they, together with the quasars, contribute about 60 percent of the observed background. About half of this is contributed by active galactic nuclei with optical luminosities below those of quasars

  19. Using quasars as standard clocks for measuring cosmological redshift.

    Science.gov (United States)

    Dai, De-Chang; Starkman, Glenn D; Stojkovic, Branislav; Stojkovic, Dejan; Weltman, Amanda

    2012-06-08

    We report hitherto unnoticed patterns in quasar light curves. We characterize segments of the quasar's light curves with the slopes of the straight lines fit through them. These slopes appear to be directly related to the quasars' redshifts. Alternatively, using only global shifts in time and flux, we are able to find significant overlaps between the light curves of different pairs of quasars by fitting the ratio of their redshifts. We are then able to reliably determine the redshift of one quasar from another. This implies that one can use quasars as standard clocks, as we explicitly demonstrate by constructing two independent methods of finding the redshift of a quasar from its light curve.

  20. The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; /Penn State U.; Richards, Gordon T.; /Drexel U.; Hall, Patrick B.; /York U., Canada; Strauss, Michael A.; /Princeton U. Observ.; Anderson, Scott F.; /Washington U., Seattle, Astron. Dept.; Boroson, Todd A.; /Kitt Peak Observ.; Ross, Nicholas P.; /Penn State U.; Shen, Yue; /Princeton U. Observ.; Brandt, W.N.; /Penn State U.; Fan, Xiaohui; /Arizona U., Astron. Dept. - Steward Observ.; Inada, Naohisa; /Wako, RIKEN /Southampton U. /Heidelberg, Max Planck Inst. Astron.

    2010-04-01

    We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog, which is based upon the SDSS Seventh Data Release. The catalog, which contains 105,783 spectroscopically confirmed quasars, represents the conclusion of the SDSS-I and SDSS-II quasar survey. The catalog consists of the SDSS objects that have luminosities larger than M{sub i} = -22.0 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or have interesting/complex absorption features, are fainter than i {approx} 15.0, and have highly reliable redshifts. The catalog covers an area of {approx} 9380 deg{sup 2}. The quasar redshifts range from 0.065 to 5.46, with a median value of 1.49; the catalog includes 1248 quasars at redshifts greater than 4, of which 56 are at redshifts greater than 5. The catalog contains 9210 quasars with i < 18; slightly over half of the entries have i < 19. For each object the catalog presents positions accurate to better than 0.1-inch rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 {angstrom} at a spectral resolution of {approx_equal} 2000; the spectra can be retrieved from the SDSS public database using the information provided in the catalog. Over 96% of the objects in the catalog were discovered by the SDSS. We also include a supplemental list of an additional 207 quasars with SDSS spectra whose archive photometric information is incomplete.

  1. Quasar Parallax: a Method for Determining Direct Geometrical Distances to Quasars

    OpenAIRE

    Elvis, Martin; Karovska, Margarita

    2002-01-01

    We describe a novel method to determine direct geometrical distances to quasars that can measure the cosmological constant, Lambda, with minimal assumptions. This method is equivalent to geometric parallax, with the `standard length' being the size of the quasar broad emission line region (BELR) as determined from the light travel time measurements of reverberation mapping. The effect of non-zero Lambda on angular diameter is large, 40% at z=2, so mapping angular diameter distances vs. redshi...

  2. Novel Chemokine-Based Immunotoxins for Potent and Selective Targeting of Cytomegalovirus Infected Cells

    DEFF Research Database (Denmark)

    Spiess, Katja; Jeppesen, Mads G.; Malmgaard-Clausen, Mikkel

    2017-01-01

    Immunotoxins as antiviral therapeutics are largely unexplored but have promising prospective due to their high selectivity potential and their unparalleled efficiency. One recent example targeted the virus-encoded G protein-coupled receptor US28 as a strategy for specific and efficient treatment ...

  3. THE SDSS-IV EXTENDED BARYON OSCILLATION SPECTROSCOPIC SURVEY: LUMINOUS RED GALAXY TARGET SELECTION

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Abhishek; Licquia, Timothy C.; Newman, Jeffrey A.; Rao, Sandhya M. [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Ross, Ashley J. [Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Dawson, Kyle S.; Bautista, Julian E.; Brownstein, Joel R. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Kneib, Jean-Paul [Laboratoire d’Astrophysique, Ecole Polytechnique Fédérale de Lausanne Observatoire de Sauverny, 1290 Versoix (Switzerland); Percival, Will J. [Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Comparat, Johan [Instituto de Física Teórica, (UAM/CSIC), Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Tinker, Jeremy L. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Schlegel, David J. [Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720 (United States); Tojeiro, Rita [School of Physics and Astronomy, St Andrews, KY16 9SS (United Kingdom); Ho, Shirley; Lang, Dustin [Bruce and Astrid McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); McBride, Cameron K. [Harvard-Smithsonian Center for Astrophysics, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States); Zhu, Guangtun Ben, E-mail: abp15@pitt.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); and others

    2016-06-01

    We describe the algorithm used to select the luminous red galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-field Infrared Survey Explorer . LRG targets are required to meet a set of color selection criteria and have z -band and i -band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (median redshift 0.71). We demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS ancillary programs to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least ∼89% of the target sample yields secure redshift measurements. We also present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reached.

  4. In silico tools used for compound selection during target-based drug discovery and development.

    Science.gov (United States)

    Caldwell, Gary W

    2015-01-01

    The target-based drug discovery process, including target selection, screening, hit-to-lead (H2L) and lead optimization stage gates, is the most common approach used in drug development. The full integration of in vitro and/or in vivo data with in silico tools across the entire process would be beneficial to R&D productivity by developing effective selection criteria and drug-design optimization strategies. This review focuses on understanding the impact and extent in the past 5 years of in silico tools on the various stage gates of the target-based drug discovery approach. There are a large number of in silico tools available for establishing selection criteria and drug-design optimization strategies in the target-based approach. However, the inconsistent use of in vitro and/or in vivo data integrated with predictive in silico multiparameter models throughout the process is contributing to R&D productivity issues. In particular, the lack of reliable in silico tools at the H2L stage gate is contributing to the suboptimal selection of viable lead compounds. It is suggested that further development of in silico multiparameter models and organizing biologists, medicinal and computational chemists into one team with a single accountable objective to expand the utilization of in silico tools in all phases of drug discovery would improve R&D productivity.

  5. Competition between color and luminance for target selection in smooth pursuit and saccadic eye movements.

    Science.gov (United States)

    Spering, Miriam; Montagnini, Anna; Gegenfurtner, Karl R

    2008-11-24

    Visual processing of color and luminance for smooth pursuit and saccadic eye movements was investigated using a target selection paradigm. In two experiments, stimuli were varied along the dimensions color and luminance, and selection of the more salient target was compared in pursuit and saccades. Initial pursuit was biased in the direction of the luminance component whereas saccades showed a relative preference for color. An early pursuit response toward luminance was often reversed to color by a later saccade. Observers' perceptual judgments of stimulus salience, obtained in two control experiments, were clearly biased toward luminance. This choice bias in perceptual data implies that the initial short-latency pursuit response agrees with perceptual judgments. In contrast, saccades, which have a longer latency than pursuit, do not seem to follow the perceptual judgment of salience but instead show a stronger relative preference for color. These substantial differences in target selection imply that target selection processes for pursuit and saccadic eye movements use distinctly different weights for color and luminance stimuli.

  6. Close companions to two high-redshift quasars

    Energy Technology Data Exchange (ETDEWEB)

    McGreer, Ian D.; Fan, Xiaohui; Bian, Fuyan [Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Strauss, Michael A. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States); Haiman, Zoltàn [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Jiang, Linhua [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Schneider, Donald P., E-mail: imcgreer@as.arizona.edu [Department of Astronomy and Astrophysics and the Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-10-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i {sub AB} = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW{sub 0} ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ∼ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ∼4.5 mag fainter than the quasar (Y {sub AB} = 25) at a separation of 0.''9. The red i {sub 775} – Y {sub 105} color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short.

  7. Sunyaev–Zel’Dovich Signal from Quasar Hosts: Implications for Detection of Quasar Feedback

    International Nuclear Information System (INIS)

    Chowdhury, Dhruba Dutta; Chatterjee, Suchetana

    2017-01-01

    Several analytic and numerical studies have indicated that the interstellar medium of a quasar host galaxy heated by feedback can contribute to a substantial secondary signal in the cosmic microwave background (CMB) through the thermal Sunyaev–Zel’dovich (SZ) effect. Recently, many groups have tried to detect this signal by cross-correlating CMB maps with quasar catalogs. Using a self-similar model for the gas in the intra-cluster medium and a realistic halo occupation distribution (HOD) prescription for quasars, we estimate the level of SZ signal from gravitational heating of quasar hosts. The bias in the host halo signal estimation due to an unconstrained high mass HOD tail and yet unknown redshift dependence of the quasar HOD restricts us from drawing any robust conclusions at low redshift ( z < 1.5) from our analysis. However, at higher redshifts ( z > 2.5), we find an excess signal in recent observations than what is predicted from our model. The excess signal could be potentially generated from additional heating due to quasar feedback.

  8. Sunyaev–Zel’Dovich Signal from Quasar Hosts: Implications for Detection of Quasar Feedback

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, Dhruba Dutta; Chatterjee, Suchetana, E-mail: dhruba.duttachowdhury@yale.edu [Department of Physics, Presidency University, Kolkata, 700073 (India)

    2017-04-10

    Several analytic and numerical studies have indicated that the interstellar medium of a quasar host galaxy heated by feedback can contribute to a substantial secondary signal in the cosmic microwave background (CMB) through the thermal Sunyaev–Zel’dovich (SZ) effect. Recently, many groups have tried to detect this signal by cross-correlating CMB maps with quasar catalogs. Using a self-similar model for the gas in the intra-cluster medium and a realistic halo occupation distribution (HOD) prescription for quasars, we estimate the level of SZ signal from gravitational heating of quasar hosts. The bias in the host halo signal estimation due to an unconstrained high mass HOD tail and yet unknown redshift dependence of the quasar HOD restricts us from drawing any robust conclusions at low redshift ( z < 1.5) from our analysis. However, at higher redshifts ( z > 2.5), we find an excess signal in recent observations than what is predicted from our model. The excess signal could be potentially generated from additional heating due to quasar feedback.

  9. Quasar Elemental Abundances at High Redshifts

    DEFF Research Database (Denmark)

    Dietrich, M.; Hamann, F.; Shields, J. C.

    2003-01-01

    the framework of the most recent photoionization models to estimate the metallicity of the gas associated with the high-z quasars. Standard photoionization parameters and the assumption of secondary nitrogen enrichment indicate an average abundance of Z/Z_sol = 4 to 5 in the line emitting gas. Assuming a time...

  10. Low resolution infrared spectra of quasars

    International Nuclear Information System (INIS)

    Soifer, B.T.; Neugebauer, G.; Oke, J.B.; Matthews, K.

    1980-01-01

    Low resolution spectra of a significant sample of quasars show that the Paschen α and Balmer line ratios do not agree with the radiative recombination case B result and vary widely within the quasars sampled. The range in Pα:Hβ ratios is a factor of approximately 6, while the range in Lyα:Hα ratios is a factor of approximately 5. For the Pα:Balmer series, the deviations from case B recombination are not consistent with reddening, but appear, within large dispersions, to be consistent with optical depth effects in the Balmer lines affecting the line ratios. The Lyα:Hα ratio is, however, correlated with the continuum spectral index, and can be explained as due to reddening affecting both the lines and continuum. Recent observational results based on a joint infrared/optical survey of the hydrogen line spectra of a significant number of the brightest low and high redshift quasars are summarised. This survey includes 12 quasars in the redshift range 0.07 1.5, where Hα and/or Hβ is redshifted into the 1.65μm or 2.2μm atmospheric windows. (Auth.)

  11. Quasar Mass Functions Across Cosmic Time

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2010-01-01

    I present mass functions of actively accreting black holes detected in different quasar surveys which in concert cover a wide range of cosmic history. I briefly address what we learn from these mass functions. I summarize the motivation for such a study and the methods by which we determine black...

  12. Quasars, Seyfert galaxies and active galactic nuclei

    International Nuclear Information System (INIS)

    Osterbrock, D.E.

    1987-01-01

    This chapter is devoted to the spectroscopic methods for analyzing the observed plasma in the nuclei of quasars, Seyfert galazies, and active galactic nuclei. Both the narrow-line region and the broad-line region are discussed. Physical models are presented

  13. Stimulus selection and tracking during urination: autoshaping directed behavior with toilet targets.

    Science.gov (United States)

    Siegel, R K

    1977-01-01

    A simple procedure is described for investigating stimuli selected as targets during urination in the commode. Ten normal males preferred a floating target that could be tracked to a series of stationary targets. This technique was used to bring misdirected urinations in a severely retarded male under rapid stimulus control of a floating target in the commode. The float stimulus was also evaluated with nine institionalized, moderately retarded males and results indicated rapid autoshaping of directed urination without the use of verbal instructions or conventional toilet training. The technique can be applied in training children to control misdirected urinations in institution for the retarded, in psychiatric wards with regressed populations, and in certain male school dormitories. PMID:885828

  14. Cross-Correlations in Quasar Radio Emission

    Science.gov (United States)

    Nefedyev, Yuri; Panischev, Oleg; Demin, Sergey

    The main factors forming the complex evolution of the accretive astrophysical systems are nonlinearity, intermittency, nonstationarity and also collective phenomena. To discover the dynamic processes in these objects and to detain understanding their properties we need to use all the applicable analyzing methods. Here we use the Flicker-Noise Spectroscopy (FNS) as a phenomenological approach to analyzing and parameterizing the auto- and cross-correlations in time series of astrophysical objects dynamics. As an example we consider the quasar flux radio spectral density at frequencies 2.7 GHz and 8.1 GHz. Data have been observed by Dr. N. Tanizuka (Laboratory for Complex Systems Analysis, Osaka Prefecture University) in a period of 1979 to 1988 (3 309 days). According to mental habits quasar is a very energetic and distant active galactic nucleus containing a supermassive black hole by size 10-10,000 times the Schwarzschild radius. The quasar is powered by an accretion disc around the black hole. The accretion disc material layers, moving around the black hole, are under the influence of gravitational and frictional forces. It results in raising the high temperature and arising the resonant and collective phenomena reflected in quasar emission dynamics. Radio emission dynamics of the quasar 0215p015 is characterized by three quasi-periodic processes, which are prevalent in considering dynamics. By contrast the 1641p399's emission dynamics have not any distinguish processes. It means the presence of high intermittency in accretive modes. The second difference moment allows comparing the degree of manifesting of resonant and chaotic components in initial time series of the quasar radio emission. The comparative analysis shows the dominating of chaotic part of 1641p399's dynamics whereas the radio emission of 0215p015 has the predominance of resonant component. Analyzing the collective features of the quasar radio emission intensity demonstrates the significant

  15. The Physical Relation between Disc and Coronal Emission in Quasars

    Directory of Open Access Journals (Sweden)

    Elisabeta Lusso

    2018-01-01

    Full Text Available We propose a modified version of the observed non-linear relation between the X-ray (2 keV and the ultraviolet (2,500 Å emission in quasars (i.e., LX∝LUVγ which involves the full width at half-maximum, FWHM, of the broad emission line, i.e., LX∝LUVγ^ FWHMβ^. By analyzing a sample of 550 optically selected non-jetted quasars in the redshift range of 0.36–2.23 from the Sloan Digital Sky Survey cross matched with the XMM-Newton catalog 3XMM-DR6, we found that the additional dependence of the observed LX − LUV correlation on the FWHM of the Mgii broad emission line is statistically significant. Our statistical analysis leads to a much tighter relation with respect to the one neglecting FWHM, and it does not evolve with redshift. We interpret this new relation within an accretion disc corona scenario where reconnection and magnetic loops above the accretion disc can account for the production of the primary X-ray radiation. For a broad line region size depending on the disc luminosity as Rblr∝Ldisc0.5, we find that LX∝LUV4/7 FWHM4/7, which is in very good agreement with the observed correlation.

  16. Evolution of Extragalactic Radio Sources and Quasar/Galaxy Unification

    Science.gov (United States)

    Onah, C. I.; Ubachukwu, A. A.; Odo, F. C.; Onuchukwu, C. C.

    2018-04-01

    We use a large sample of radio sources to investigate the effects of evolution, luminosity selection and radio source orientation in explaining the apparent deviation of observed angular size - redshift (θ - z) relation of extragalactic radio sources (EGRSs) from the standard model. We have fitted the observed θ - z data with standard cosmological models based on a flat universe (Ω0 = 1). The size evolution of EGRSs has been described as luminosity, temporal and orientation-dependent in the form DP,z,Φ ≍ P±q(1 + z)-m sinΦ, with q=0.3, Φ=59°, m=-0.26 for radio galaxies and q=-0.5, Φ=33°, m=3.1 for radio quasars respectively. Critical points of luminosity, logPcrit=26.33 WHz-1 and logDc=2.51 kpc (316.23 kpc) of the present sample of radio sources were also observed. All the results were found to be consistent with the popular quasar/galaxy unification scheme.

  17. SDSS J2222+2745: A GRAVITATIONALLY LENSED SEXTUPLE QUASAR WITH A MAXIMUM IMAGE SEPARATION OF 15.''1 DISCOVERED IN THE SLOAN GIANT ARCS SURVEY

    International Nuclear Information System (INIS)

    Dahle, H.; Groeneboom, N.; Gladders, M. D.; Abramson, L. E.; Sharon, K.; Bayliss, M. B.; Wuyts, E.; Koester, B. P.; Brinckmann, T. E.; Kristensen, M. T.; Lindholmer, M. O.; Nielsen, A.; Krogager, J.-K.; Fynbo, J. P. U.

    2013-01-01

    We report the discovery of a unique gravitational lens system, SDSS J2222+2745, producing five spectroscopically confirmed images of a z s = 2.82 quasar lensed by a foreground galaxy cluster at z l = 0.49. We also present photometric and spectroscopic evidence for a sixth lensed image of the same quasar. The maximum separation between the quasar images is 15.''1. Both the large image separations and the high image multiplicity are in themselves rare among known lensed quasars, and observing the combination of these two factors is an exceptionally unlikely occurrence in present data sets. This is only the third known case of a quasar lensed by a cluster, and the only one with six images. The lens system was discovered in the course of the Sloan Giant Arcs Survey, in which we identify candidate lenses in the Sloan Digital Sky Survey and target these for follow-up and verification with the 2.56 m Nordic Optical Telescope. Multi-band photometry obtained over multiple epochs from 2011 September to 2012 September reveals significant variability at the ∼10%-30% level in some of the quasar images, indicating that measurements of the relative time delay between quasar images will be feasible. In this lens system, we also identify a bright (g = 21.5) giant arc corresponding to a strongly lensed background galaxy at z s = 2.30. We fit parametric models of the lens system, constrained by the redshift and positions of the quasar images and the redshift and position of the giant arc. The predicted time delays between different pairs of quasar images range from ∼100 days to ∼6 yr

  18. Band selection method based on spectrum difference in targets of interest in hyperspectral imagery

    Science.gov (United States)

    Zhang, Xiaohan; Yang, Guang; Yang, Yongbo; Huang, Junhua

    2016-10-01

    While hyperspectral data shares rich spectrum information, it has numbers of bands with high correlation coefficients, causing great data redundancy. A reasonable band selection is important for subsequent processing. Bands with large amount of information and low correlation should be selected. On this basis, according to the needs of target detection applications, the spectral characteristics of the objects of interest are taken into consideration in this paper, and a new method based on spectrum difference is proposed. Firstly, according to the spectrum differences of targets of interest, a difference matrix which represents the different spectral reflectance of different targets in different bands is structured. By setting a threshold, the bands satisfying the conditions would be left, constituting a subset of bands. Then, the correlation coefficients between bands are calculated and correlation matrix is given. According to the size of the correlation coefficient, the bands can be set into several groups. At last, the conception of normalized variance is used on behalf of the information content of each band. The bands are sorted by the value of its normalized variance. Set needing number of bands, and the optimum band combination solution can be get by these three steps. This method retains the greatest degree of difference between the target of interest and is easy to achieve by computer automatically. Besides, false color image synthesis experiment is carried out using the bands selected by this method as well as other 3 methods to show the performance of method in this paper.

  19. Engineering Multi-Walled Carbon Nanotube Therapeutic Bionanofluids to Selectively Target Papillary Thyroid Cancer Cells.

    Directory of Open Access Journals (Sweden)

    Idit Dotan

    Full Text Available The incidence of papillary thyroid carcinoma (PTC has risen steadily over the past few decades as well as the recurrence rates. It has been proposed that targeted ablative physical therapy could be a therapeutic modality in thyroid cancer. Targeted bio-affinity functionalized multi-walled carbon nanotubes (BioNanofluid act locally, to efficiently convert external light energy to heat thereby specifically killing cancer cells. This may represent a promising new cancer therapeutic modality, advancing beyond conventional laser ablation and other nanoparticle approaches.Thyroid Stimulating Hormone Receptor (TSHR was selected as a target for PTC cells, due to its wide expression. Either TSHR antibodies or Thyrogen or purified TSH (Thyrotropin were chemically conjugated to our functionalized Bionanofluid. A diode laser system (532 nm was used to illuminate a PTC cell line for set exposure times. Cell death was assessed using Trypan Blue staining.TSHR-targeted BioNanofluids were capable of selectively ablating BCPAP, a TSHR-positive PTC cell line, while not TSHR-null NSC-34 cells. We determined that a 2:1 BCPAP cell:α-TSHR-BioNanofluid conjugate ratio and a 30 second laser exposure killed approximately 60% of the BCPAP cells, while 65% and >70% of cells were ablated using Thyrotropin- and Thyrogen-BioNanofluid conjugates, respectively. Furthermore, minimal non-targeted killing was observed using selective controls.A BioNanofluid platform offering a potential therapeutic path for papillary thyroid cancer has been investigated, with our in vitro results suggesting the development of a potent and rapid method of selective cancer cell killing. Therefore, BioNanofluid treatment emphasizes the need for new technology to treat patients with local recurrence and metastatic disease who are currently undergoing either re-operative neck explorations, repeated administration of radioactive iodine and as a last resort external beam radiation or chemotherapy, with

  20. In vitro Selection and Interaction Studies of a DNA Aptamer Targeting Protein A.

    Directory of Open Access Journals (Sweden)

    Regina Stoltenburg

    Full Text Available A new DNA aptamer targeting Protein A is presented. The aptamer was selected by use of the FluMag-SELEX procedure. The SELEX technology (Systematic Evolution of Ligands by EXponential enrichment is widely applied as an in vitro selection and amplification method to generate target-specific aptamers and exists in various modified variants. FluMag-SELEX is one of them and is characterized by the use of magnetic beads for target immobilization and fluorescently labeled oligonucleotides for monitoring the aptamer selection progress. Structural investigations and sequence truncation experiments of the selected aptamer for Protein A led to the conclusion, that a stem-loop structure at its 5'-end including the 5'-primer binding site is essential for aptamer-target binding. Extensive interaction analyses between aptamer and Protein A were performed by methods like surface plasmon resonance, MicroScale Thermophoresis and bead-based binding assays using fluorescence measurements. The binding of the aptamer to its target was thus investigated in assays with immobilization of one of the binding partners each, and with both binding partners in solution. Affinity constants were determined in the low micromolar to submicromolar range, increasing to the nanomolar range under the assumption of avidity. Protein A provides more than one binding site for the aptamer, which may overlap with the known binding sites for immunoglobulins. The aptamer binds specifically to both native and recombinant Protein A, but not to other immunoglobulin-binding proteins like Protein G and L. Cross specificity to other proteins was not found. The application of the aptamer is directed to Protein A detection or affinity purification. Moreover, whole cells of Staphylococcus aureus, presenting Protein A on the cell surface, could also be bound by the aptamer.

  1. In vitro Selection and Interaction Studies of a DNA Aptamer Targeting Protein A.

    Science.gov (United States)

    Stoltenburg, Regina; Schubert, Thomas; Strehlitz, Beate

    2015-01-01

    A new DNA aptamer targeting Protein A is presented. The aptamer was selected by use of the FluMag-SELEX procedure. The SELEX technology (Systematic Evolution of Ligands by EXponential enrichment) is widely applied as an in vitro selection and amplification method to generate target-specific aptamers and exists in various modified variants. FluMag-SELEX is one of them and is characterized by the use of magnetic beads for target immobilization and fluorescently labeled oligonucleotides for monitoring the aptamer selection progress. Structural investigations and sequence truncation experiments of the selected aptamer for Protein A led to the conclusion, that a stem-loop structure at its 5'-end including the 5'-primer binding site is essential for aptamer-target binding. Extensive interaction analyses between aptamer and Protein A were performed by methods like surface plasmon resonance, MicroScale Thermophoresis and bead-based binding assays using fluorescence measurements. The binding of the aptamer to its target was thus investigated in assays with immobilization of one of the binding partners each, and with both binding partners in solution. Affinity constants were determined in the low micromolar to submicromolar range, increasing to the nanomolar range under the assumption of avidity. Protein A provides more than one binding site for the aptamer, which may overlap with the known binding sites for immunoglobulins. The aptamer binds specifically to both native and recombinant Protein A, but not to other immunoglobulin-binding proteins like Protein G and L. Cross specificity to other proteins was not found. The application of the aptamer is directed to Protein A detection or affinity purification. Moreover, whole cells of Staphylococcus aureus, presenting Protein A on the cell surface, could also be bound by the aptamer.

  2. Design, construction, and characterization of high-performance membrane fusion devices with target-selectivity.

    Science.gov (United States)

    Kashiwada, Ayumi; Yamane, Iori; Tsuboi, Mana; Ando, Shun; Matsuda, Kiyomi

    2012-01-31

    Membrane fusion proteins such as the hemagglutinin glycoprotein have target recognition and fusion accelerative domains, where some synergistically working elements are essential for target-selective and highly effective native membrane fusion systems. In this work, novel membrane fusion devices bearing such domains were designed and constructed. We selected a phenylboronic acid derivative as a recognition domain for a sugar-like target and a transmembrane-peptide (Leu-Ala sequence) domain interacting with the target membrane, forming a stable hydrophobic α-helix and accelerating the fusion process. Artificial membrane fusion behavior between the synthetic devices in which pilot and target liposomes were incorporated was characterized by lipid-mixing and inner-leaflet lipid-mixing assays. Consequently, the devices bearing both the recognition and transmembrane domains brought about a remarkable increase in the initial rate for the membrane fusion compared with the devices containing the recognition domain alone. In addition, a weakly acidic pH-responsive device was also constructed by replacing three Leu residues in the transmembrane-peptide domain by Glu residues. The presence of Glu residues made the acidic pH-dependent hydrophobic α-helix formation possible as expected. The target-selective liposome-liposome fusion was accelerated in a weakly acidic pH range when the Glu-substituted device was incorporated in pilot liposomes. The use of this pH-responsive device seems to be a potential strategy for novel applications in a liposome-based delivery system. © 2011 American Chemical Society

  3. Out with the old? The role of selective attention in retaining targets in partial report.

    Science.gov (United States)

    Lindsey, Dakota R B; Bundesen, Claus; Kyllingsbæk, Søren; Petersen, Anders; Logan, Gordon D

    2017-01-01

    In the partial-report task, subjects are asked to report only a portion of the items presented. Selective attention chooses which objects to represent in short-term memory (STM) on the basis of their relevance. Because STM is limited in capacity, one must sometimes choose which objects are removed from memory in light of new relevant information. We tested the hypothesis that the choices among newly presented information and old information in STM involve the same process-that both are acts of selective attention. We tested this hypothesis using a two-display partial-report procedure. In this procedure, subjects had to select and retain relevant letters (targets) from two sequentially presented displays. If selection in perception and retention in STM are the same process, then irrelevant letters (distractors) in the second display, which demanded attention because of their similarity to the targets, should have decreased target report from the first display. This effect was not obtained in any of four experiments. Thus, choosing objects to keep in STM is not the same process as choosing new objects to bring into STM.

  4. Evolution of radio quasars from redshift 0.6-3.7

    International Nuclear Information System (INIS)

    Neff, S.G.; Hutchings, J.B.

    1990-01-01

    This paper presents the results of VLA radio imaging of 58 radio-loud quasars with redshift 2.0 or higher, which fill the redshift-luminosity plane as evenly as possible. This work completes a survey of about 250 quasars covering redshifts from 0.6-3.7, which attempts to sample luminosity and look-back time in a uniform way. Within the constraints of possible selection effects it is found that the relative population of extended and unresolved sources changes with redshift in a way that suggests that radio quasars may live longer and spend more time as large triple sources in the present epoch than in the earlier universe. There appear to be few low-luminosity radio quasars at high redshift. Ejection of material appears to occur on one side at a time, with usually at least one reversal of direction in the source lifetime. The velocity of ejection appears to be mildly relativistic at high redshift, but of lower velocity in the present epoch. There is also evidence suggestive of changes in the IGM with cosmic time; however, the data presented do not show the minimum in density at z about 2 that has been suggested for cluster environments. 11 refs

  5. C IV BROAD ABSORPTION LINE ACCELERATION IN SLOAN DIGITAL SKY SURVEY QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Grier, C. J.; Brandt, W. N.; Trump, J. R.; Schneider, D. P.; Sun, M.; Beatty, T. G. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Hall, P. B. [Department of Physics and Astronomy, York University, Toronto, ON M3J 1P3 (Canada); Filiz Ak, N. [Faculty of Sciences, Department of Astronomy and Space Sciences, Erciyes University, 38039 Kayseri (Turkey); Anderson, S. F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Green, Paul J. [Harvard Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Vivek, M.; Brownstein, Joel R. [Department of Physics and Astronomy, University of Utah, 115 S. 1400 E., Salt Lake City, UT 84112 (United States); Roman-Lopes, Alexandre, E-mail: grier@psu.edu [Departamento de Fisica, Facultad de Ciencias, Universidad de La Serena, Cisternas 1200, La Serena (Chile)

    2016-06-20

    We present results from the largest systematic investigation of broad absorption line (BAL) acceleration to date. We use spectra of 140 quasars from three Sloan Digital Sky Survey programs to search for global velocity offsets in BALs over timescales of ≈2.5–5.5 years in the quasar rest frame. We carefully select acceleration candidates by requiring monolithic velocity shifts over the entire BAL trough, avoiding BALs with velocity shifts that might be caused by profile variability. The C iv BALs of two quasars show velocity shifts consistent with the expected signatures of BAL acceleration, and the BAL of one quasar shows a velocity-shift signature of deceleration. In our two acceleration candidates, we see evidence that the magnitude of the acceleration is not constant over time; the magnitudes of the change in acceleration for both acceleration candidates are difficult to produce with a standard disk-wind model or via geometric projection effects. We measure upper limits to acceleration and deceleration for 76 additional BAL troughs and find that the majority of BALs are stable to within about 3% of their mean velocities. The lack of widespread acceleration/deceleration could indicate that the gas producing most BALs is located at large radii from the central black hole and/or is not currently strongly interacting with ambient material within the host galaxy along our line of sight.

  6. Selective whole genome amplification for resequencing target microbial species from complex natural samples.

    Science.gov (United States)

    Leichty, Aaron R; Brisson, Dustin

    2014-10-01

    Population genomic analyses have demonstrated power to address major questions in evolutionary and molecular microbiology. Collecting populations of genomes is hindered in many microbial species by the absence of a cost effective and practical method to collect ample quantities of sufficiently pure genomic DNA for next-generation sequencing. Here we present a simple method to amplify genomes of a target microbial species present in a complex, natural sample. The selective whole genome amplification (SWGA) technique amplifies target genomes using nucleotide sequence motifs that are common in the target microbe genome, but rare in the background genomes, to prime the highly processive phi29 polymerase. SWGA thus selectively amplifies the target genome from samples in which it originally represented a minor fraction of the total DNA. The post-SWGA samples are enriched in target genomic DNA, which are ideal for population resequencing. We demonstrate the efficacy of SWGA using both laboratory-prepared mixtures of cultured microbes as well as a natural host-microbe association. Targeted amplification of Borrelia burgdorferi mixed with Escherichia coli at genome ratios of 1:2000 resulted in >10(5)-fold amplification of the target genomes with genomic extracts from Wolbachia pipientis-infected Drosophila melanogaster resulted in up to 70% of high-throughput resequencing reads mapping to the W. pipientis genome. By contrast, 2-9% of sequencing reads were derived from W. pipientis without prior amplification. The SWGA technique results in high sequencing coverage at a fraction of the sequencing effort, thus allowing population genomic studies at affordable costs. Copyright © 2014 by the Genetics Society of America.

  7. Weak hard X-ray emission from two broad absorption line quasars observed with NuSTAR: Compton-thick absorption or intrinsic X-ray weakness?

    DEFF Research Database (Denmark)

    Luo, B.; Brandt, W. N.; Alexander, D. M.

    2013-01-01

    are not significantly absorbed (NH ≲ 1024 cm-2). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain...... likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place...

  8. Specific and selective target detection of supra-genome 21 Mers Salmonella via silicon nanowires biosensor

    Science.gov (United States)

    Mustafa, Mohammad Razif Bin; Dhahi, Th S.; Ehfaed, Nuri. A. K. H.; Adam, Tijjani; Hashim, U.; Azizah, N.; Mohammed, Mohammed; Noriman, N. Z.

    2017-09-01

    The nano structure based on silicon can be surface modified to be used as label-free biosensors that allow real-time measurements. The silicon nanowire surface was functionalized using 3-aminopropyltrimethoxysilane (APTES), which functions as a facilitator to immobilize biomolecules on the silicon nanowire surface. The process is simple, economical; this will pave the way for point-of-care applications. However, the surface modification and subsequent detection mechanism still not clear. Thus, study proposed step by step process of silicon nano surface modification and its possible in specific and selective target detection of Supra-genome 21 Mers Salmonella. The device captured the molecule with precisely; the approach took the advantages of strong binding chemistry created between APTES and biomolecule. The results indicated how modifications of the nanowires provide sensing capability with strong surface chemistries that can lead to specific and selective target detection.

  9. Designing the nanobiointerface of fluorescent nanodiamonds: highly selective targeting of glioma cancer cells.

    Science.gov (United States)

    Slegerova, Jitka; Hajek, Miroslav; Rehor, Ivan; Sedlak, Frantisek; Stursa, Jan; Hruby, Martin; Cigler, Petr

    2015-01-14

    Core-shell nanoparticles based on fluorescent nanodiamonds coated with a biocompatible N-(2-hydroxypropyl)methacrylamide copolymer shell were developed for background-free near-infrared imaging of cancer cells. The particles showed excellent colloidal stability in buffers and culture media. After conjugation with a cyclic RGD peptide they selectively targeted integrin αvβ3 receptors on glioblastoma cells with high internalization efficacy.

  10. Mature Epitope Density - A strategy for target selection based on immunoinformatics and exported prokaryotic proteins

    DEFF Research Database (Denmark)

    Santos, Anderson R; Pereira, Vanessa Bastos; Barbosa, Eudes

    2013-01-01

    . However, currently available tools do not account for the concentration of epitope products in the mature protein product and its relation to the reliability of target selection. RESULTS: We developed a computational strategy based on measuring the epitope's concentration in the mature protein, called...... Mature Epitope Density (MED). Our method, though simple, is capable of identifying promising vaccine targets. Our online software implementation provides a computationally light and reliable analysis of bacterial exoproteins and their potential for vaccines or diagnosis projects against pathogenic...... proteins were confirmed as related. There was no experimental evidence of antigenic or pathogenic contributions for three of the highest MED-scored Mtb proteins. Hence, these three proteins could represent novel putative vaccine and drug targets for Mtb. A web version of MED is publicly available online...

  11. Social comparisons in adults with type 2 diabetes: Patients' reasons for target selection.

    Science.gov (United States)

    Arigo, Danielle; Cornell, Max; Smyth, Joshua M

    2018-07-01

    To examine reasons for selecting a social comparison target (i.e. a specific other for relative self-evaluation), and their influence on affect and motivation for self-care, in type 2 diabetes (T2DM). Adults with T2DM (n = 180, M A1c  = 7.6%) chose to read about one of four targets. Participants rated five reasons for their choice (strongly disagree - strongly agree), and rated affect and self-care motivation before and after reading. To boost confidence in my ability to manage diabetes was rated highest overall (ps motivation (p motivation only among those who chose better-off targets (p = 0.01). Patients' reasons for a particular comparison are associated with short-term changes in affect and self-care motivation, and warrant greater empirical and clinical attention.

  12. Promysalin Elicits Species-Selective Inhibition of Pseudomonas aeruginosa by Targeting Succinate Dehydrogenase.

    Science.gov (United States)

    Keohane, Colleen E; Steele, Andrew D; Fetzer, Christian; Khowsathit, Jittasak; Van Tyne, Daria; Moynié, Lucile; Gilmore, Michael S; Karanicolas, John; Sieber, Stephan A; Wuest, William M

    2018-02-07

    Natural products have served as an inspiration to scientists both for their complex three-dimensional architecture and exquisite biological activity. Promysalin is one such Pseudomonad secondary metabolite that exhibits narrow-spectrum antibacterial activity, originally isolated from the rhizosphere. We herein utilize affinity-based protein profiling (AfBPP) to identify succinate dehydrogenase (Sdh) as the biological target of the natural product. The target was further validated in silico, in vitro, in vivo, and through the selection, and sequencing, of a resistant mutant. Succinate dehydrogenase plays an essential role in primary metabolism of Pseudomonas aeruginosa as the only enzyme that is involved both in the tricarboxylic acid cycle (TCA) and in respiration via the electron transport chain. These findings add credence to other studies that suggest that the TCA cycle is an understudied target in the development of novel therapeutics to combat P. aeruginosa, a significant pathogen in clinical settings.

  13. The TESS Input Catalog and Selection of Targets for the TESS Transit Search

    Science.gov (United States)

    Pepper, Joshua; Stassun, Keivan G.; Paegert, Martin; Oelkers, Ryan; De Lee, Nathan Michael; Torres, Guillermo; TESS Target Selection Working Group

    2018-01-01

    The TESS mission will photometrically survey millions of the brightest stars over almost the entire the sky to detect transiting exoplanets. A key step to enable that search is the creation of the TESS Input Catalog (TIC), a compiled catalog of 700 million stars and galaxies with observed and calculated parameters. From the TIC we derive the Candidate Target List (CTL) to identify target stars for the 2-minute TESS postage stamps. The CTL is designed to identify the best stars for the detection of small planets, which includes all bright cool dwarf stars in the sky. I will describe the target selection strategy, the distribution of stars in the current CTL, and how both the TIC and CTL will expand and improve going forward.

  14. Targeting hunter distribution based on host resource selection and kill sites to manage disease risk.

    Science.gov (United States)

    Dugal, Cherie J; van Beest, Floris M; Vander Wal, Eric; Brook, Ryan K

    2013-10-01

    Endemic and emerging diseases are rarely uniform in their spatial distribution or prevalence among cohorts of wildlife. Spatial models that quantify risk-driven differences in resource selection and hunter mortality of animals at fine spatial scales can assist disease management by identifying high-risk areas and individuals. We used resource selection functions (RSFs) and selection ratios (SRs) to quantify sex- and age-specific resource selection patterns of collared (n = 67) and hunter-killed (n = 796) nonmigratory elk (Cervus canadensis manitobensis) during the hunting season between 2002 and 2012, in southwestern Manitoba, Canada. Distance to protected area was the most important covariate influencing resource selection and hunter-kill sites of elk (AICw = 1.00). Collared adult males (which are most likely to be infected with bovine tuberculosis (Mycobacterium bovis) and chronic wasting disease) rarely selected for sites outside of parks during the hunting season in contrast to adult females and juvenile males. The RSFs showed selection by adult females and juvenile males to be negatively associated with landscape-level forest cover, high road density, and water cover, whereas hunter-kill sites of these cohorts were positively associated with landscape-level forest cover and increasing distance to streams and negatively associated with high road density. Local-level forest was positively associated with collared animal locations and hunter-kill sites; however, selection was stronger for collared juvenile males and hunter-killed adult females. In instances where disease infects a metapopulation and eradication is infeasible, a principle goal of management is to limit the spread of disease among infected animals. We map high-risk areas that are regularly used by potentially infectious hosts but currently underrepresented in the distribution of kill sites. We present a novel application of widely available data to target hunter distribution based on host resource

  15. Diversity of soft X-ray spectra in quasars

    International Nuclear Information System (INIS)

    Elvis, M.; Wilkes, B.J.; Tananbaum, H.

    1985-01-01

    Soft X-ray spectra for three quasars obtained with the Einstein Imaging Proportional Counter covering the 0.1-4.0 keV band are reported. Power-law fits to these spectra have best-fit energy indices of 1.2 +0.6 or -0.2, for the quasar NAB 0205 + 024, 0.6 +0.3 or -0.2 for the quasar B2 1028 + 313, and 2.2 + or -0.4 for the quasar PG 1211 + 143. None of the quasars shows any evidence for a column density of cold matter in excess of the galactic values. The derived spectra demonstrate that there is no single universal power law slope for quasar X-ray spectra. The implications of these results for the X-ray background, X-ray continuum emission mechanisms, and the production of the optical/UV emission lines are briefly discussed. 46 references

  16. Summary of the workshop on active galaxies and quasars

    International Nuclear Information System (INIS)

    Weistrop, D.

    1981-01-01

    The paper reports highlights of discussions carried out at the Tenth Texas Symposium on Relativistic Astrophysics concerning BL Lacertae objects and quasars and their relationship to active galactic nuclei. The discussions considered X-ray, optical and radio observations of active galaxies and quasars showing features which may be interpreted as jets or beams, and X-ray and VLBI observations of core-jet structures exhibiting apparent supraluminal expansion. Attention was also given to the properties of the energy source in the center of the active galaxies and quasars, the nature of quasar emission line regions, the production of the continuum in quasars and active galactic nuclei, and evidence for the association of quasars and BL Lac objects with galaxies

  17. Retroviral DNA integration: viral and cellular determinants of target-site selection.

    Directory of Open Access Journals (Sweden)

    Mary K Lewinski

    2006-06-01

    Full Text Available Retroviruses differ in their preferences for sites for viral DNA integration in the chromosomes of infected cells. Human immunodeficiency virus (HIV integrates preferentially within active transcription units, whereas murine leukemia virus (MLV integrates preferentially near transcription start sites and CpG islands. We investigated the viral determinants of integration-site selection using HIV chimeras with MLV genes substituted for their HIV counterparts. We found that transferring the MLV integrase (IN coding region into HIV (to make HIVmIN caused the hybrid to integrate with a specificity close to that of MLV. Addition of MLV gag (to make HIVmGagmIN further increased the similarity of target-site selection to that of MLV. A chimeric virus with MLV Gag only (HIVmGag displayed targeting preferences different from that of both HIV and MLV, further implicating Gag proteins in targeting as well as IN. We also report a genome-wide analysis indicating that MLV, but not HIV, favors integration near DNase I-hypersensitive sites (i.e., +/- 1 kb, and that HIVmIN and HIVmGagmIN also favored integration near these features. These findings reveal that IN is the principal viral determinant of integration specificity; they also reveal a new role for Gag-derived proteins, and strengthen models for integration targeting based on tethering of viral IN proteins to host proteins.

  18. Chlorin e6 Conjugated Interleukin-6 Receptor Aptamers Selectively Kill Target Cells Upon Irradiation

    Directory of Open Access Journals (Sweden)

    Sven Kruspe

    2014-01-01

    Full Text Available Photodynamic therapy (PDT uses the therapeutic properties of light in combination with certain chemicals, called photosensitizers, to successfully treat brain, breast, prostate, and skin cancers. To improve PDT, current research focuses on the development of photosensitizers to specifically target cancer cells. In the past few years, aptamers have been developed to directly deliver cargo molecules into target cells. We conjugated the photosensitizer chlorin e6 (ce6 with a human interleukin-6 receptor (IL-6R binding RNA aptamer, AIR-3A yielding AIR-3A-ce6 for application in high efficient PDT. AIR-3A-ce6 was rapidly and specifically internalized by IL-6R presenting (IL-6R+ cells. Upon light irradiation, targeted cells were selectively killed, while free ce6 did not show any toxic effect. Cells lacking the IL-6R were also not affected by AIR-3A-ce6. With this approach, we improved the target specificity of ce6-mediated PDT. In the future, other tumor-specific aptamers might be used to selectively localize photosensitizers into cells of interest and improve the efficacy and specificity of PDT in cancer and other diseases.

  19. Selection of RIB targets using ion implantation at the Holifield radioactive ion beam facility

    International Nuclear Information System (INIS)

    Alton, G.D.; Dellwo, J.

    1995-01-01

    Among several major challenges posed by generating and accelerating adequate intensities of RIBs, selection of the most appropriate target material is perhaps the most difficult because of the requisite fast and selective thermal release of minute amounts of the short-lived product atoms from the ISOL target in the presence of bulk amounts of target material. Experimental studies are under way at the Oak Ridge National Laboratory (ORNL) which are designed to measure the time evolution of implanted elements diffused from refractory target materials which are candidates for forming radioactive ion beams (RIBs) at the Holifield Radioactive Ion Beam Facility (HRIBF). The diffusion coefficients are derived by comparing experimental data with numerical solutions to a one-dimensional form of Fick's second law for ion implanted distributions. In this report, we describe the experimental arrangement, experimental procedures, and provide time release data and diffusion coefficients for releasing ion implanted 37 Cl from Zr 5 Si 3 and 75 As, 79 Br, and 78 Se from Zr 5 Ge 3 and estimates of the diffusion coefficients for 35 Cl, 63 Cu, 65 Cu, 69 Ga and 71 Ga diffused from BN; 35 Cl, 63 Cu, 65 Cu, 69 Ga, 75 As, and 78 Se diffused from C; 35 Cl, 68 Cu, 69 Ga, 75 As, and 78 Se diffused from Ta

  20. Efficient and Adaptive Node Selection for Target Tracking in Wireless Sensor Network

    Directory of Open Access Journals (Sweden)

    Juan Feng

    2016-01-01

    Full Text Available In target tracking wireless sensor network, choosing the proper working nodes can not only minimize the number of active nodes, but also satisfy the tracking reliability requirement. However, most existing works focus on selecting sensor nodes which are the nearest to the target for tracking missions and they did not consider the correlation of the location of the sensor nodes so that these approaches can not meet all the goals of the network. This work proposes an efficient and adaptive node selection approach for tracking a target in a distributed wireless sensor network. The proposed approach combines the distance-based node selection strategy and particle filter prediction considering the spatial correlation of the different sensing nodes. Moreover, a joint distance weighted measurement is proposed to estimate the information utility of sensing nodes. Experimental results show that EANS outperformed the state-of-the-art approaches by reducing the energy cost and computational complexity as well as guaranteeing the tracking accuracy.

  1. Merger and Acquisition Target Selection Based on Interval Neutrosophic Multigranulation Rough Sets over Two Universes

    Directory of Open Access Journals (Sweden)

    Chao Zhang

    2017-07-01

    Full Text Available As a significant business activity, merger and acquisition (M&A generally means transactions in which the ownership of companies, other business organizations or their operating units are transferred or combined. In a typical M&A procedure, M&A target selection is an important issue that tends to exert an increasingly significant impact on different business areas. Although some research works based on fuzzy methods have been explored on this issue, they can only deal with incomplete and uncertain information, but not inconsistent and indeterminate information that exists universally in the decision making process. Additionally, it is advantageous to solve M&A problems under the group decision making context. In order to handle these difficulties in M&A target selection background, we introduce a novel rough set model by combining interval neutrosophic sets (INSs with multigranulation rough sets over two universes, called an interval neutrosophic (IN multigranulation rough set over two universes. Then, we discuss the definition and some fundamental properties of the proposed model. Finally, we establish decision making rules and computing approaches for the proposed model in M&A target selection background, and the effectiveness of the decision making approach is demonstrated by an illustrative case analysis.

  2. A Peptidomimetic Antibiotic Targets Outer Membrane Proteins and Disrupts Selectively the Outer Membrane in Escherichia coli.

    Science.gov (United States)

    Urfer, Matthias; Bogdanovic, Jasmina; Lo Monte, Fabio; Moehle, Kerstin; Zerbe, Katja; Omasits, Ulrich; Ahrens, Christian H; Pessi, Gabriella; Eberl, Leo; Robinson, John A

    2016-01-22

    Increasing antibacterial resistance presents a major challenge in antibiotic discovery. One attractive target in Gram-negative bacteria is the unique asymmetric outer membrane (OM), which acts as a permeability barrier that protects the cell from external stresses, such as the presence of antibiotics. We describe a novel β-hairpin macrocyclic peptide JB-95 with potent antimicrobial activity against Escherichia coli. This peptide exhibits no cellular lytic activity, but electron microscopy and fluorescence studies reveal an ability to selectively disrupt the OM but not the inner membrane of E. coli. The selective targeting of the OM probably occurs through interactions of JB-95 with selected β-barrel OM proteins, including BamA and LptD as shown by photolabeling experiments. Membrane proteomic studies reveal rapid depletion of many β-barrel OM proteins from JB-95-treated E. coli, consistent with induction of a membrane stress response and/or direct inhibition of the Bam folding machine. The results suggest that lethal disruption of the OM by JB-95 occurs through a novel mechanism of action at key interaction sites within clusters of β-barrel proteins in the OM. These findings open new avenues for developing antibiotics that specifically target β-barrel proteins and the integrity of the Gram-negative OM. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  3. Selective autophagy of non-ubiquitylated targets in plants: looking for cognate receptor/adaptor proteins

    Directory of Open Access Journals (Sweden)

    Vasko eVeljanovski

    2014-06-01

    Full Text Available Cellular homeostasis is essential for the physiology of eukaryotic cells. Eukaryotic cells, including plant cells, utilize two main pathways to adjust the level of cytoplasmic components, namely the proteasomal and the lysosomal/vacuolar pathways. Macroautophagy is a lysosomal/vacuolar pathway which, until recently, was thought to be non-specific and a bulk degradation process. However, selective autophagy which can be activated in the cell under various physiological conditions, involves the specific degradation of defined macromolecules or organelles by a conserved molecular mechanism. For this process to be efficient, the mechanisms underlying the recognition and selection of the cargo to be engulfed by the double-membrane autophagosome are critical, and not yet well understood. Ubiquitin (poly-ubiquitin conjugation to the target appears to be a conserved ligand mechanism in many types of selective autophagy, and defined receptors/adaptors recognizing and regulating the autophagosomal capture of the ubiquitylated target have been characterized. However, non-proteinaceous and non-ubiquitylated cargoes are also selectively degraded by this pathway. This ubiquitin-independent selective autophagic pathway also involves receptor and/or adaptor proteins linking the cargo to the autophagic machinery. Some of these receptor/adaptor proteins including accessory autophagy-related (Atg and non-Atg proteins have been described in yeast and animal cells but not yet in plants. In this review we discuss the ubiquitin-independent cargo selection mechanisms in selective autophagy degradation of organelles and macromolecules and speculate on potential plant receptor/adaptor proteins.

  4. A Search for Radio-loud Quasars within the Epoch of Reionization

    OpenAIRE

    Jarvis, Matt J.; Rawlings, Steve; Barrio, F. Eugenio; Hill, Gary J.; Bauer, Amanda; Croft, Steve

    2003-01-01

    The Universe became fully reionized, and observable optically, at a time corresponding to redshift z~6.5, so it is only by studying the HI and molecular absorption lines against higher-redshift, radio-loud sources that one can hope to make detailed studies of the earliest stages of galaxy formation. At present no targets for such studies are known. In these proceedings we describe a survey which is underway to find radio-loud quasars at z > 6.5.

  5. THE TIME DOMAIN SPECTROSCOPIC SURVEY: VARIABLE SELECTION AND ANTICIPATED RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Morganson, Eric; Green, Paul J. [Harvard Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Eracleous, Michael; Brandt, William Nielsen [Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States); Kelly, Brandon [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530 (United States); Badenes, Carlos [Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara St, Pittsburgh, PA 15260 (United States); Bañados, Eduardo [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 N. Charter St., Madison, WI 53706 (United States); Borissova, Jura [Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, and Millennium Institute of Astrophysics (MAS), Santiago (Chile); Burgett, William S. [GMTO Corp, Suite 300, 251 S. Lake Ave, Pasadena, CA 91101 (United States); Chambers, Kenneth, E-mail: emorganson@cfa.harvard.edu [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); and others

    2015-06-20

    We present the selection algorithm and anticipated results for the Time Domain Spectroscopic Survey (TDSS). TDSS is an Sloan Digital Sky Survey (SDSS)-IV Extended Baryon Oscillation Spectroscopic Survey (eBOSS) subproject that will provide initial identification spectra of approximately 220,000 luminosity-variable objects (variable stars and active galactic nuclei across 7500 deg{sup 2} selected from a combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be the largest spectroscopic survey to explicitly target variable objects, avoiding pre-selection on the basis of colors or detailed modeling of specific variability characteristics. Kernel Density Estimate analysis of our target population performed on SDSS Stripe 82 data suggests our target sample will be 95% pure (meaning 95% of objects we select have genuine luminosity variability of a few magnitudes or more). Our final spectroscopic sample will contain roughly 135,000 quasars and 85,000 stellar variables, approximately 4000 of which will be RR Lyrae stars which may be used as outer Milky Way probes. The variability-selected quasar population has a smoother redshift distribution than a color-selected sample, and variability measurements similar to those we develop here may be used to make more uniform quasar samples in large surveys. The stellar variable targets are distributed fairly uniformly across color space, indicating that TDSS will obtain spectra for a wide variety of stellar variables including pulsating variables, stars with significant chromospheric activity, cataclysmic variables, and eclipsing binaries. TDSS will serve as a pathfinder mission to identify and characterize the multitude of variable objects that will be detected photometrically in even larger variability surveys such as Large Synoptic Survey Telescope.

  6. Target Selection and Deselection at the Berkeley StructuralGenomics Center

    Energy Technology Data Exchange (ETDEWEB)

    Chandonia, John-Marc; Kim, Sung-Hou; Brenner, Steven E.

    2005-03-22

    At the Berkeley Structural Genomics Center (BSGC), our goalis to obtain a near-complete structural complement of proteins in theminimal organisms Mycoplasma genitalium and M. pneumoniae, two closelyrelated pathogens. Current targets for structure determination have beenselected in six major stages, starting with those predicted to be mosttractable to high throughput study and likely to yield new structuralinformation. We report on the process used to select these proteins, aswell as our target deselection procedure. Target deselection reducesexperimental effort by eliminating targets similar to those recentlysolved by the structural biology community or other centers. We measurethe impact of the 69 structures solved at the BSGC as of July 2004 onstructure prediction coverage of the M. pneumoniae and M. genitaliumproteomes. The number of Mycoplasma proteins for which thefold couldfirst be reliably assigned based on structures solved at the BSGC (24 M.pneumoniae and 21 M. genitalium) is approximately 25 percent of the totalresulting from work at all structural genomics centers and the worldwidestructural biology community (94 M. pneumoniae and 86M. genitalium)during the same period. As the number of structures contributed by theBSGC during that period is less than 1 percent of the total worldwideoutput, the benefits of a focused target selection strategy are apparent.If the structures of all current targets were solved, the percentage ofM. pneumoniae proteins for which folds could be reliably assigned wouldincrease from approximately 57 percent (391 of 687) at present to around80 percent (550 of 687), and the percentage of the proteome that could beaccurately modeled would increase from around 37 percent (254 of 687) toabout 64 percent (438 of 687). In M. genitalium, the percentage of theproteome that could be structurally annotated based on structures of ourremaining targets would rise from 72 percent (348 of 486) to around 76percent (371 of 486), with the

  7. The DESI Experiment Part I: Science,Targeting, and Survey Design

    Energy Technology Data Exchange (ETDEWEB)

    Aghamousa, Amir; et al.

    2016-10-31

    DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. To trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. We will measure luminous red galaxies up to $z=1.0$. To probe the Universe out to even higher redshift, DESI will target bright [O II] emission line galaxies up to $z=1.7$. Quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts ($ 2.1 < z < 3.5$), for the Ly-$\\alpha$ forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. When moonlight prevents efficient observations of the faint targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey comprising approximately 10 million galaxies with a median $z\\approx 0.2$. In total, more than 30 million galaxy and quasar redshifts will be obtained to measure the BAO feature and determine the matter power spectrum, including redshift space distortions.

  8. Implications of structural genomics target selection strategies: Pfam5000, whole genome, and random approaches

    Energy Technology Data Exchange (ETDEWEB)

    Chandonia, John-Marc; Brenner, Steven E.

    2004-07-14

    The structural genomics project is an international effort to determine the three-dimensional shapes of all important biological macromolecules, with a primary focus on proteins. Target proteins should be selected according to a strategy which is medically and biologically relevant, of good value, and tractable. As an option to consider, we present the Pfam5000 strategy, which involves selecting the 5000 most important families from the Pfam database as sources for targets. We compare the Pfam5000 strategy to several other proposed strategies that would require similar numbers of targets. These include including complete solution of several small to moderately sized bacterial proteomes, partial coverage of the human proteome, and random selection of approximately 5000 targets from sequenced genomes. We measure the impact that successful implementation of these strategies would have upon structural interpretation of the proteins in Swiss-Prot, TrEMBL, and 131 complete proteomes (including 10 of eukaryotes) from the Proteome Analysis database at EBI. Solving the structures of proteins from the 5000 largest Pfam families would allow accurate fold assignment for approximately 68 percent of all prokaryotic proteins (covering 59 percent of residues) and 61 percent of eukaryotic proteins (40 percent of residues). More fine-grained coverage which would allow accurate modeling of these proteins would require an order of magnitude more targets. The Pfam5000 strategy may be modified in several ways, for example to focus on larger families, bacterial sequences, or eukaryotic sequences; as long as secondary consideration is given to large families within Pfam, coverage results vary only slightly. In contrast, focusing structural genomics on a single tractable genome would have only a limited impact in structural knowledge of other proteomes: a significant fraction (about 30-40 percent of the proteins, and 40-60 percent of the residues) of each proteome is classified in small

  9. Mean and extreme radio properties of quasars and the origin of radio emission

    Energy Technology Data Exchange (ETDEWEB)

    Kratzer, Rachael M.; Richards, Gordon T. [Department of Physics, Drexel University, Philadelphia, PA (United States)

    2015-02-01

    We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.

  10. NuSTAR observations of heavily obscured quasars at z ∼ 0.5

    Energy Technology Data Exchange (ETDEWEB)

    Lansbury, G. B.; Alexander, D. M.; Moro, A. Del; Gandhi, P.; Aird, J. [Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Assef, R. J. [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Baloković, M.; Grefenstette, B. W.; Harrison, F. A. [Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Catlica de Chile, Casilla 306, Santiago 22 (Chile); Boggs, S. E. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Christensen, F. E.; Craig, W. W. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Elvis, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hailey, C. J. [Columbia Astrophysics Laboratory, 550 W 120th Street, Columbia University, NY 10027 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Koss, M., E-mail: g.b.lansbury@durham.ac.uk [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); and others

    2014-04-10

    We present NuSTAR hard X-ray observations of three Type 2 quasars at z ≈ 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O III] luminosity ratio and multiwavelength diagnostics, their X-ray absorbing column densities (N {sub H}) are poorly known. In this analysis, (1) we study X-ray emission at >10 keV, where X-rays from the central black hole are relatively unabsorbed, in order to better constrain N {sub H}. (2) We further characterize the physical properties of the sources through broad-band near-UV to mid-IR spectral energy distribution analyses. One of the quasars is detected with NuSTAR at >8 keV with a no-source probability of <0.1%, and its X-ray band ratio suggests near Compton-thick absorption with N {sub H} ≳ 5 × 10{sup 23} cm{sup –2}. The other two quasars are undetected, and have low X-ray to mid-IR luminosity ratios in both the low-energy (2-10 keV) and high-energy (10-40 keV) X-ray regimes that are consistent with extreme, Compton-thick absorption (N {sub H} ≳ 10{sup 24} cm{sup –2}). We find that for quasars at z ∼ 0.5, NuSTAR provides a significant improvement compared to lower energy (<10 keV) Chandra and XMM-Newton observations alone, as higher column densities can now be directly constrained.

  11. NuSTAR Reveals Extreme Absorption in z < 0.5 Type 2 Quasars

    Science.gov (United States)

    Lansbury, G. B.; Gandhi, P.; Alexander, D. M.; Assef, R. J.; Aird, J.; Annuar, A.; Ballantyne, D. R.; Baloković, M.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Civano, F.; Comastri, A.; Craig, W. W.; Del Moro, A.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Koss, M.; LaMassa, S. M.; Luo, B.; Puccetti, S.; Stern, D.; Treister, E.; Vignali, C.; Zappacosta, L.; Zhang, W. W.

    2015-08-01

    The intrinsic column density (NH) distribution of quasars is poorly known. At the high obscuration end of the quasar population and for redshifts z 1.5 × 1024 cm-2) type 2 quasars (CTQSO2s); five new NuSTAR observations are reported herein, and four have been previously published. The candidate CTQSO2s lie at z < 0.5, have observed [O iii] luminosities in the range 8.4\\lt {log}({L}[{{O} {{III}}]}/{L}⊙ )\\lt 9.6, and show evidence for extreme, Compton-thick absorption when indirect absorption diagnostics are considered. Among the nine candidate CTQSO2s, five are detected by NuSTAR in the high-energy (8-24 keV) band: two are weakly detected at the ≈3σ confidence level and three are strongly detected with sufficient counts for spectral modeling (≳90 net source counts at 8-24 keV). For these NuSTAR-detected sources direct (i.e., X-ray spectral) constraints on the intrinsic active galactic nucleus properties are feasible, and we measure column densities ≈2.5-1600 times higher and intrinsic (unabsorbed) X-ray luminosities ≈10-70 times higher than pre-NuSTAR constraints from Chandra and XMM-Newton. Assuming the NuSTAR-detected type 2 quasars are representative of other Compton-thick candidates, we make a correction to the NH distribution for optically selected type 2 quasars as measured by Chandra and XMM-Newton for 39 objects. With this approach, we predict a Compton-thick fraction of {f}{CT}={36}-12+14 %, although higher fractions (up to 76%) are possible if indirect absorption diagnostics are assumed to be reliable.

  12. The Sloan Digital Sky Survey Quasar Catalog. 3. Third data release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; Hall, Patrick B.; Richards, Gordon T.; Vanden Berk, Daniel E.; Anderson, Scott F.; Fan, Xiao-Hui; Jester, Sebastian; Stoughton, Chris; Strauss,; SubbaRao, Mark; Brandt, W.N.; Gunn, James E.; Yanny, Brian; Bahcall, Neta A.; Barentine, J.C.; Blanton, Michael R.; Boroski, William N.; Brewington, Howard J.; Brinkmann, J.; Brunner, Robert; Csabai, Istvan; /Penn State U., Astron. Astrophys. /York U., Canada /Princeton U. Observ. /Washington U., Seattle, Astron. Dept. /Arizona U.,

    2005-03-01

    We present the third edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 46,420 objects in the SDSS Third Data Release that have luminosities larger than M{sub i} = -22 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or are unambiguously broad absorption line quasars, are fainter than i = 15.0, and have highly reliable redshifts. The area covered by the catalog is {approx} 4188 deg{sup 2}. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.47; the high-redshift sample includes 520 quasars at redshifts greater than four, of which 17 are at redshifts greater than five. For each object the catalog presents positions accurate to better than 0.2'' rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 at a spectral resolution of {approx} 2000; the spectra can be retrieved from the public database using the information provided in the catalog. A total of 44,221 objects in the catalog were discovered by the SDSS; 28,400 of the SDSS discoveries are reported here for the first time.

  13. The diffusion properties of ion implanted species in selected target materials

    International Nuclear Information System (INIS)

    Alton, G.D.; Dellwo, J.; Carter, H.K.; Kormicki, J.; Bartolo, G. di; Batchelder, J.C.; Breitenbach, J.; Chediak, J.A.; Jentoff-Nilsen, K.; Ichikawa, S.

    1995-01-01

    Experiments important to the future success of the Holifield Radioactive Ion Beam Facility (HRIBF) are in progress at the Oak Ridge National Laboratory which are designed to select the most appropriate target material for generating a particular radioactive ion beam (RIB). The 25-MV HHIRF tandem accelerator is used to implant stable complements of interesting radioactive elements into refractory targets mounted in a high-temperature FEBIAD ion source which is open-quotes on-lineclose quotes at the UNISOR facility. The intensity versus time of implanted species, which diffuse from the high-temperature target material (∼1700 degrees C) and are ionized in the FEBIAD ion source, is used to determine release times for a particular projectile/target material combination. From such release data, diffusion coefficients can be derived by fitting the theoretical results obtained by computational solution of Fick's second equation to experimental data. The diffusion coefficient can be used subsequently to predict the release properties of the particular element from the same material in other target geometries and at other temperatures, provided that the activation energy is also known. Diffusion coefficients for Cl implanted into and diffused from CeS and Zr 5 Si 3 and As, Br, and Se implanted into and diffused from Zr 5 Ge 3 have been derived from the resulting intensity versus time profiles. Brief descriptions of the experimental apparatus and procedures utilized in the present experiments and plans for future related experiments are presented

  14. Companions of low-redshift radio-quiet quasars

    International Nuclear Information System (INIS)

    Yee, H.K.C.

    1987-01-01

    Using imaging data from a relatively complete subset of low-redshift radio-quiet quasars, the frequency of finding associated companion galaxies of the quasars is determined statistically. With an average completeness limit of M/sub r/ of about -19, it is found that about 40 percent of the quasars have at least one close physical companion within a projected distance of 100 kpc. The percentage of quasars with detected companions is consistent with all quasars in the sample having a companion of luminosity brighter than about -16.5 mag. It is estimated that the frequency of finding close companions to quasars is about six times higher than that expected for field galaxies. This frequency is similar to that found for lower-luminosity Seyfert galaxies. The properties of the companions appear to be uncorrelated with the level of activity in the quasars. This suggests that, for radio-quiet quasars, the companions act mainly as triggers of the activity and are probably not a strong determining factor of the detailed properties of the quasars. 28 references

  15. Intrinsic variations of the double quasar 0957 + 56 AB

    International Nuclear Information System (INIS)

    Lloyd, C.

    1981-01-01

    Observations of the two components of the quasar 0957 + 56A and B are reported which show a variation of approximately 1 mag in both components and behaviour typical of intrinsically variable quasars with similar radio structure. It is argued that the near constancy of the magnitude difference between the components at several epochs, despite overall variations, favours all the variations being intrinsic to the quasar and also supports the hypothesis that the two images are produced by the gravitational lensing of a single distant quasar. (U.K.)

  16. An explanation of the mysterious quasars

    International Nuclear Information System (INIS)

    Borissov, O.

    1977-01-01

    The article presents details of a convincing new theory submitted by Russian scientists, concerning the physical nature of quasars. These were discovered in 1963 and for over ten years no satisfactory theory has been forthcoming to explain their seemingly incompatible properties or the associated phenomena. These very distant objects are believed to be sources of the most powerful electromagnetic emission. From the new theory expounded it is concluded that for the first time since their discovery a satisfactory explanation of their nature has been reached. From this it is hoped that the mechanism of energy generation by quasars may ultimately be understood and, though on a much reduced scale, contribute to the solution of energy problems on earth. (R.J.J.)

  17. Automated analysis of slitless spectra. II. Quasars

    International Nuclear Information System (INIS)

    Edwards, G.; Beauchemin, M.; Borra, F.

    1988-01-01

    Automated software have been developed to process slitless spectra. The software, described in a previous paper, automatically separates stars from extended objects and quasars from stars. This paper describes the quasar search techniques and discusses the results. The performance of the software is compared and calibrated with a plate taken in a region of SA 57 that has been extensively surveyed by others using a variety of techniques: the proposed automated software performs very well. It is found that an eye search of the same plate is less complete than the automated search: surveys that rely on eye searches suffer from incompleteness at least from a magnitude brighter than the plate limit. It is shown how the complete automated analysis of a plate and computer simulations are used to calibrate and understand the characteristics of the present data. 20 references

  18. Black hole accretion: the quasar powerhouse

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    A program is described which calculates the effects of material falling into the curved space-time surrounding a rotation black hole. The authors have developed a two-dimensional, general-relativistic hydrodynamics code to simulate fluid flow in the gravitational field of a rotating black hole. Such calculations represent models that have been proposed for the energy sources of both quasars and jets from radiogalaxies. In each case, the black hole that powers the quasar or jet would have a mass of about 100 million times the mass of the sun. The black hole would be located in the center of a galaxy whose total mass is 1000 time greater than the black hole mass. (SC)

  19. Microlensing of quasar ultraviolet iron emission

    Energy Technology Data Exchange (ETDEWEB)

    Guerras, E.; Mediavilla, E. [Instituto de Astrofísica de Canarias, Vía Láctea S/N, La Laguna 38200, Tenerife (Spain); Jimenez-Vicente, J. [Departamento de Física Teórica y del Cosmos, Universidad de Granada, Campus de Fuentenueva, 18071 Granada (Spain); Kochanek, C. S. [Department of Astronomy and the Center for Cosmology and Astroparticle Physics, The Ohio State University, 4055 McPherson Lab, 140 West 18th Avenue, Columbus, OH 43221 (United States); Muñoz, J. A. [Departamento de Astronomía y Astrofísica, Universidad de Valencia, 46100 Burjassot, Valencia (Spain); Falco, E. [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Motta, V.; Rojas, K. [Departamento de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso (Chile)

    2013-12-01

    We measure the differential microlensing of the UV Fe II and Fe III emission line blends between 14 quasar image pairs in 13 gravitational lenses. We find that the UV iron emission is strongly microlensed in four cases with amplitudes comparable to that of the continuum. Statistically modeling the magnifications, we infer a typical size of r{sub s}∼4√(M/M{sub ⊙}) light-days for the Fe line-emitting regions, which is comparable to the size of the region generating the UV continuum (∼3-7 light-days). This may indicate that a significant part of the UV Fe II and Fe III emission originates in the quasar accretion disk.

  20. Do quasar ley lines really exist

    International Nuclear Information System (INIS)

    Webster, A.

    1982-01-01

    The hypothesis that the distribution of the quasars on the celestial sphere contains an unexpectedly large number of well-aligned triples is tested by applying, to the Cerro Tololo objective-prism sample, a shape-statistic which was originally developed to investigate whether neolithic standing stones were deliberately sited on ley lines. It is found that alignment in triples is not a conspicuous feature of the quasars in this sample. The sample does contain one well aligned triple whose properties resemble those of two triples found earlier in a different field by earlier authors, but the probability of this being a chance alignment is not low. The same authors have noted a total of four well-collimated triples which they consider remarkable, but an approximate probability calculation based on the shape-statistic indicates that they need not have a low probability of occurring by chance. (author)

  1. Infrared observations of Seyfert galaxies and quasars

    International Nuclear Information System (INIS)

    Neugebauer, G.

    1978-01-01

    The infrared energy distributions of the Seyfert galaxies apparently contain three components: a galactic stellar component, a thermal component from heated dust, plus a nonthermal component. The appearance of the infrared energy distribution depends on which component dominates. There is also a correlation observed between the infrared energy distribution and the Khachikian Weedman class. Preliminary data on bright quasars are given. The infrared energy distributions generally increase into the infrared with a power law slope of approximately 1. In detail they differ from power laws with a significant fraction emitting most of their energy near 3μm. No differences in radio loud and radio quiet are obvious from the infrared energy distributions. The variability of the quasars in the infrared is generally correlated with the variability in the visible, although significant exceptions have been observed. (Auth.)

  2. Quasars in the Life of Astronomers

    Science.gov (United States)

    D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W.; Collin, Suzy; Setti, Giancarlo; Gaskell, Martin; Wampler, Joe; Elvis, Martin; Pronik, Iraida; Pronik, Vladimir; Sergeev, Sergey; Volvach, Aleksander; Krolik, Julian; Netzer, Hagai; Cavaliere, Alfonso; Padovani, Paolo; Arp, Halton; Narlikar, Jayant

    We are approaching the 50th anniversary of the discovery of quasars. Those old enough to have been cognizant of astronomy in 1962-1963 can remember the sense of excitement connected with this finding. There was talk of a major new constituent of the universe. The excitement of the discovery was palpable even to one of us (the most senior of the editors) who was then a high school teenager.

  3. Selective Inhibition of Histone Deacetylation in Melanoma Increases Targeted Gene Delivery by a Bacteriophage Viral Vector

    Directory of Open Access Journals (Sweden)

    Samuel Campbell

    2018-04-01

    Full Text Available The previously developed adeno-associated virus/phage (AAVP vector, a hybrid between M13 bacteriophage (phage viruses that infect bacteria only and human Adeno-Associated Virus (AAV, is a promising tool in targeted gene therapy against cancer. AAVP can be administered systemically and made tissue specific through the use of ligand-directed targeting. Cancer cells and tumor-associated blood vessels overexpress the αν integrin receptors, which are involved in tumor angiogenesis and tumor invasion. AAVP is targeted to these integrins via a double cyclic RGD4C ligand displayed on the phage capsid. Nevertheless, there remain significant host-defense hurdles to the use of AAVP in targeted gene delivery and subsequently in gene therapy. We previously reported that histone deacetylation in cancer constitutes a barrier to AAVP. Herein, to improve AAVP-mediated gene delivery to cancer cells, we combined the vector with selective adjuvant chemicals that inhibit specific histone deacetylases (HDAC. We examined the effects of the HDAC inhibitor C1A that mainly targets HDAC6 and compared this to sodium butyrate, a pan-HDAC inhibitor with broad spectrum HDAC inhibition. We tested the effects on melanoma, known for HDAC6 up-regulation, and compared this side by side with a normal human kidney HEK293 cell line. Varying concentrations were tested to determine cytotoxic levels as well as effects on AAVP gene delivery. We report that the HDAC inhibitor C1A increased AAVP-mediated transgene expression by up to ~9-fold. These findings indicate that selective HDAC inhibition is a promising adjuvant treatment for increasing the therapeutic value of AAVP.

  4. Hunting for Intrinsically X-ray Weak Quasars: The Case of PHL 1811 Analogs

    Science.gov (United States)

    Brandt, William

    2009-09-01

    A central dogma of X-ray astronomy is that luminous X-ray emission is a universal property of efficiently accreting supermassive black holes. One interesting challenge to this idea has come from the quasar PHL 1811 which appears to be intrinsically X-ray weak and also has distinctive emission-line properties. We propose to observe a sample of eight SDSS quasars, selected to have similar UV emission-line properties to that of PHL 1811, to test if they are also X-ray weak. Our analyses of the currently available X-ray data appear to support this hypothesis but do not provide a proper test. Our results will have implications for the nature of accretion-disk coronae, emission-line formation, and AGN selection.

  5. Star formation in active galaxies and quasars

    International Nuclear Information System (INIS)

    Heckman, T.M.

    1987-01-01

    I review the observational evidence for a causal or statistical link between star formation and active galactic nuclei. The chief difficulty is in quantitatively ascertaining the star formation rate in active galaxies: most of the readily observable manifestations of star formation superficially resemble those of an active nucleus. Careful multi-wavelength spatially-resolved observations demonstrate that many Seyfert galaxies are undergoing star formation. Our survey of CO emission from Seyferts (interpreted in conjunction IRAS data) suggests that type 2 Seyferts have unusually high rates of star formation, but type 1 Seyferts do not. Recent work also suggests that many powerful radio galaxies may be actively forming stars: radio galaxies with strong emission-lines often have blue colors and strong far-infrared emission. Determining the star formation rate in the host galaxies of quasars is especially difficult. Multi-color imaging and long-slit spectroscopy suggests that many of the host galaxies of radio-loud quasars are blue and a cold interstellar medium has been detected in some quasar hosts

  6. Reverberation Mapping of High-Luminosity Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Kaspi, Shai [Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv (Israel); Brandt, William N. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA (United States); Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA (United States); Department of Physics, Pennsylvania State University, University Park, PA (United States); Maoz, Dan; Netzer, Hagai [Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv (Israel); Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA (United States); Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA (United States); Shemmer, Ohad, E-mail: shai@wise.tau.ac.il [Department of Physics, University of North Texas, Denton, TX (United States)

    2017-10-30

    Over the past three decades reverberation mapping (RM) has been applied to about 100 AGNs. Their broad line region (BLR) sizes were measured and yielded mass estimates of the black holes in their center. However, very few attempts were carried out for high-luminosity quasars, at luminosities higher than 10{sup 46} erg/sec in the optical. Most of these attempts failed since RM of such quasars is difficult due to a number of reasons, mostly due to the long time needed to monitor these objects. During the past two decades we carried out a RM campaign on six high-luminosity quasars. This contribution presents some of the final light curves of that RM campaign in which we measured the BLR size in C iv of three of the objects (S5 0836+71, SBS 1116+603, and SBS 1425+606). We present the C iv BLR size and luminosity relation over eight orders of magnitude in luminosity, pushing the luminosity limit to its highest point so far.

  7. Quasar Massive Ionized Outflows Traced by CIV λ1549 and [OIII]λλ4959,5007

    Energy Technology Data Exchange (ETDEWEB)

    Marziani, Paola [National Institute for Astrophysics, Osservatorio Astronomico di Padova, Rome (Italy); Negrete, C. Alenka; Dultzin, Deborah [Instituto de Astronomía, Universidad Nacional Autonoma de Mexico, Mexico City (Mexico); Martínez-Aldama, Mary L.; Del Olmo, Ascensión [Instituto de Astrofísica de Andalucía (CSIC), Granada (Spain); D' Onofrio, Mauro [Dipartimento di Fisica e Astronomia, Università di Padova, Padova (Italy); Stirpe, Giovanna M., E-mail: paola.marziani@oapd.inaf.it [Osservatorio Astronomico di Bologna (INAF), Bologna (Italy)

    2017-09-27

    The most luminous quasars (with bolometric luminosities are ≳ 10{sup 47} erg/s) show a high prevalence of CIV λ1549 and [OIII]λλ4959,5007 emission line profiles with strong blueshifts. Blueshifts are interpreted as due to Doppler effect and selective obscuration, and indicate outflows occurring over a wide range of spatial scales. We found evidence in favor of the nuclear origin of the outflows diagnosed by [OIII]λλ4959,5007. The ionized gas mass, kinetic power, and mechanical thrust are extremely high, and suggest widespread feedback effects on the host galaxies of very luminous quasars, at cosmic epochs between 2 and 6 Gyr from the Big Bang. In this mini-review we summarize results obtained by our group and reported in several major papers in the last few years with an eye on challenging aspects of quantifying feedback effects in large samples of quasars.

  8. Quasar Massive Ionized Outflows Traced by CIV λ1549 and [OIII]λλ4959,5007

    Directory of Open Access Journals (Sweden)

    Paola Marziani

    2017-09-01

    Full Text Available The most luminous quasars (with bolometric luminosities are ≳ 1047 erg/s show a high prevalence of CIV λ1549 and [OIII]λλ4959,5007 emission line profiles with strong blueshifts. Blueshifts are interpreted as due to Doppler effect and selective obscuration, and indicate outflows occurring over a wide range of spatial scales. We found evidence in favor of the nuclear origin of the outflows diagnosed by [OIII]λλ4959,5007. The ionized gas mass, kinetic power, and mechanical thrust are extremely high, and suggest widespread feedback effects on the host galaxies of very luminous quasars, at cosmic epochs between 2 and 6 Gyr from the Big Bang. In this mini-review we summarize results obtained by our group and reported in several major papers in the last few years with an eye on challenging aspects of quantifying feedback effects in large samples of quasars.

  9. A dual selection based, targeted gene replacement tool for Magnaporthe grisea and Fusarium oxysporum.

    Science.gov (United States)

    Khang, Chang Hyun; Park, Sook-Young; Lee, Yong-Hwan; Kang, Seogchan

    2005-06-01

    Rapid progress in fungal genome sequencing presents many new opportunities for functional genomic analysis of fungal biology through the systematic mutagenesis of the genes identified through sequencing. However, the lack of efficient tools for targeted gene replacement is a limiting factor for fungal functional genomics, as it often necessitates the screening of a large number of transformants to identify the desired mutant. We developed an efficient method of gene replacement and evaluated factors affecting the efficiency of this method using two plant pathogenic fungi, Magnaporthe grisea and Fusarium oxysporum. This method is based on Agrobacterium tumefaciens-mediated transformation with a mutant allele of the target gene flanked by the herpes simplex virus thymidine kinase (HSVtk) gene as a conditional negative selection marker against ectopic transformants. The HSVtk gene product converts 5-fluoro-2'-deoxyuridine to a compound toxic to diverse fungi. Because ectopic transformants express HSVtk, while gene replacement mutants lack HSVtk, growing transformants on a medium amended with 5-fluoro-2'-deoxyuridine facilitates the identification of targeted mutants by counter-selecting against ectopic transformants. In addition to M. grisea and F. oxysporum, the method and associated vectors are likely to be applicable to manipulating genes in a broad spectrum of fungi, thus potentially serving as an efficient, universal functional genomic tool for harnessing the growing body of fungal genome sequence data to study fungal biology.

  10. Peering through the dust: NuSTAR observations of two first-2MASS red quasars

    DEFF Research Database (Denmark)

    LaMassa, Stephanie M.; Ricarte, Angelo; Glikman, Eilat

    2016-01-01

    through this gas and dust, revealing the properties of circumnuclear obscuration. Here, we present NuSTAR and XMM-Newton/Chandra observations of FIRST-2MASS-selected red quasars F2M 0830+3759 and F2M 1227+3214. We find that though F2M 0830+3759 is moderately obscured (NH,Z = (2.1 ± 0.2) ×  1022 cm−2...

  11. Perceptions of similarity and response to selected comparison targets in type 2 diabetes.

    Science.gov (United States)

    Arigo, Danielle; Smyth, Joshua M; Suls, Jerry M

    2015-01-01

    Social comparisons (i.e. self-evaluations relative to others) may affect motivation for diabetes self-care behaviours. Comparisons can have either positive or negative effects, but it is not clear what differentiates these responses. This study tested the effect of a patient's perceived similarity to a comparison target on motivation for self-care. Individuals with type 2 diabetes (n = 180, MA1c = 7.59%) selected to read one of four brief descriptions of a patient with diabetes. Participants rated their motivation for self-care behaviours prior and subsequent to reading and reported the extent to which they focused on similarities between the self and the selected patient while reading. Perceived similarity moderated the effect of selection on motivation for self-care (p = .01, η2 = .06). Increased motivation was observed if participants focused on similarities with patients 'doing better' (i.e. high coping effectiveness/low symptom severity) and decreased motivation if they focused on similarities with patients 'doing worse' (low coping effectiveness/high symptom severity). Providing social comparison information in diabetes management (and perhaps other chronic diseases) may improve motivation for self-care among some patients. A subset of patients, however, may benefit from guidance to focus on similarities with certain targets.

  12. The optical variability of SDSS quasars from multi-epoch spectroscopy. I. Results from 60 quasars with ≥ six-epoch spectra

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hengxiao; Gu, Minfeng, E-mail: hxguo@shao.ac.cn, E-mail: gumf@shao.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

    2014-09-01

    In a sample of 60 quasars selected from the Sloan Digital Sky Survey with at least six-epoch spectroscopy, we investigate the variability of emission lines and continuum luminosity at various aspects. A strong anti-correlation between the variability and continuum luminosity at 2500 Å is found for the sample, which is consistent with previous works. In individual sources, we find that half of the sample objects follow the trend of being bluer when brighter, while the remaining half follow the redder-when-brighter (RWB) trend. Although the mechanism for RWB is unclear, the effects of host galaxy contribution due to seeing variations cannot be completely ruled out. As expected from the photoionization model, the positive correlations between the broad emission line and continuum luminosity are found in most individual sources, as well as for the whole sample. We confirm the Baldwin effect in most individual objects and the whole sample, while a negative Baldwin effect is also found in several quasars, which can be at least partly (if not all) due to the host galaxy contamination. We find positive correlations between the broad emission line luminosity and line width in most individual quasars, as well as the whole sample, implying a line base that is more variable than the line core.

  13. Antisense oligonucleotides targeting translation inhibitory elements in 5' UTRs can selectively increase protein levels.

    Science.gov (United States)

    Liang, Xue-Hai; Sun, Hong; Shen, Wen; Wang, Shiyu; Yao, Joyee; Migawa, Michael T; Bui, Huynh-Hoa; Damle, Sagar S; Riney, Stan; Graham, Mark J; Crooke, Rosanne M; Crooke, Stanley T

    2017-09-19

    A variety of diseases are caused by deficiencies in amounts or activity of key proteins. An approach that increases the amount of a specific protein might be of therapeutic benefit. We reasoned that translation could be specifically enhanced using trans-acting agents that counter the function of negative regulatory elements present in the 5' UTRs of some mRNAs. We recently showed that translation can be enhanced by antisense oligonucleotides (ASOs) that target upstream open reading frames. Here we report the amount of a protein can also be selectively increased using ASOs designed to hybridize to other translation inhibitory elements in 5' UTRs. Levels of human RNASEH1, LDLR, and ACP1 and of mouse ACP1 and ARF1 were increased up to 2.7-fold in different cell types and species upon treatment with chemically modified ASOs targeting 5' UTR inhibitory regions in the mRNAs encoding these proteins. The activities of ASOs in enhancing translation were sequence and position dependent and required helicase activity. The ASOs appear to improve the recruitment of translation initiation factors to the target mRNA. Importantly, ASOs targeting ACP1 mRNA significantly increased the level of ACP1 protein in mice, suggesting that this approach has therapeutic and research potentials. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  14. "Killer" Microcapsules That Can Selectively Destroy Target Microparticles in Their Vicinity.

    Science.gov (United States)

    Arya, Chandamany; Oh, Hyuntaek; Raghavan, Srinivasa R

    2016-11-02

    We have developed microscale polymer capsules that are able to chemically degrade a certain type of polymeric microbead in their immediate vicinity. The inspiration here is from the body's immune system, where killer T cells selectively destroy cancerous cells or cells infected by pathogens while leaving healthy cells alone. The "killer" capsules are made from the cationic biopolymer chitosan by a combination of ionic cross-linking (using multivalent tripolyposphate anions) and subsequent covalent cross-linking (using glutaraldehyde). During capsule formation, the enzyme glucose oxidase (GOx) is encapsulated in these capsules. The target beads are made by ionic cross-linking of the biopolymer alginate using copper (Cu 2+ ) cations. The killer capsules harvest glucose from their surroundings, which is then enzymatically converted by GOx into gluconate ions. These ions are known for their ability to chelate Cu 2+ cations. Thus, when a killer capsule is next to a target alginate bead, the gluconate ions diffuse into the bead and extract the Cu 2+ cross-links, causing the disintegration of the target bead. Such destruction is visualized in real-time using optical microscopy. The destruction is specific, i.e., other microparticles that do not contain Cu 2+ are left undisturbed. Moreover, the destruction is localized, i.e., the targets destroyed in the short term are the ones right next to the killer beads. The time scale for destruction depends on the concentration of encapsulated enzyme in the capsules.

  15. Seeking the epoch of maximum luminosity for dusty quasars

    International Nuclear Information System (INIS)

    Vardanyan, Valeri; Weedman, Daniel; Sargsyan, Lusine

    2014-01-01

    Infrared luminosities νL ν (7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 quasar Gpc –3 having νL ν (7.8 μm) > 10 46.6 erg s –1 for all 2 quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νL ν (0.25 μm), have the largest values of the ratio νL ν (0.25 μm)/νL ν (7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define 'obscured' quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ∼ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ∼ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  16. Selection of target mutation in rat gastrointestinal tract E. coli by minute dosage of enrofloxacin.

    Science.gov (United States)

    Lin, Dachuan; Chen, Kaichao; Li, Ruichao; Liu, Lizhang; Guo, Jiubiao; Yao, Wen; Chen, Sheng

    2014-01-01

    It has been suggested that bacterial resistance is selected within a mutation selection window of antibiotics. More recent studies showed that even extremely low concentration of antibiotic could select resistant bacteria in vitro. Yet little is known about the exact antibiotic concentration range that can effectively select for resistant organisms in animal gastrointestinal (GI) tract. In this study, the effect of different dosages of enrofloxacin on resistance and mutation development in rat GI tract E. coli was investigated by determining the number of resistant E. coli recoverable from rat fecal samples. Our data showed that high dose antibiotic treatment could effectively eliminate E. coli with single gyrA mutation in the early course of treatment, yet the eradication effects diminished upon prolonged treatment. Therapeutic and sub-therapeutic dose (1/10 and 1/100 of therapeutic doses) of enrofloxacin could effectively select for mutation in GI tract E. coli at the later course of enrofloxacin treatment and during the cessation periods. Surprisingly, very low dose of enrofloxacin (1/1000 therapeutic dose) could also select for mutation in GI tract E. coli at the later course of enrofloxacin treatment, only with slightly lower efficiency. No enrofloxacin-resistant E. coli could be selected at all test levels of enrofloxacin during long term treatment and the strength of antibiotic treatment does not alter the overall level of E. coli in rat GI tract. This study demonstrated that long term antibiotic treatment seems to be the major trigger for the development of target mutations in GI tract E. coli, which provided insight into the rational use of antibiotics in animal husbandry.

  17. Target selection and mass estimation for manned NEO exploration using a baseline mission design

    Science.gov (United States)

    Boden, Ralf C.; Hein, Andreas M.; Kawaguchi, Junichiro

    2015-06-01

    In recent years Near-Earth Objects (NEOs) have received an increased amount of interest as a target for human exploration. NEOs offer scientifically interesting targets, and at the same time function as a stepping stone for achieving future Mars missions. The aim of this research is to identify promising targets from the large number of known NEOs that qualify for a manned sample-return mission with a maximum duration of one year. By developing a baseline mission design and a mass estimation model, mission opportunities are evaluated based on on-orbit mass requirements, safety considerations, and the properties of the potential targets. A selection of promising NEOs is presented and the effects of mission requirements and restrictions are discussed. Regarding safety aspects, the use of free-return trajectories provides the lowest on-orbit mass, when compared to an alternative design that uses system redundancies to ensure return of the spacecraft to Earth. It is discovered that, although a number of targets are accessible within the analysed time frame, no NEO offers both easy access and high incentive for its exploration. Under the discussed aspects a first human exploration mission going beyond the vicinity of Earth will require a trade off between targets that provide easy access and those that are of scientific interest. This lack of optimal mission opportunities can be seen in the small number of only 4 NEOs that meet all requirements for a sample-return mission and remain below an on-orbit mass of 500 metric Tons (mT). All of them require a mass between 315 and 492 mT. Even less ideal, smaller asteroids that are better accessible require an on-orbit mass that exceeds the launch capability of future heavy lift vehicles (HLV) such as SLS by at least 30 mT. These mass requirements show that additional efforts are necessary to increase the number of available targets and reduce on-orbit mass requirements through advanced mission architectures. The need for on

  18. Target-matched insertion gain derived from three different hearing aid selection procedures.

    Science.gov (United States)

    Punch, J L; Shovels, A H; Dickinson, W W; Calder, J H; Snead, C

    1995-11-01

    Three hearing aid selection procedures were compared to determine if any one was superior in producing prescribed real-ear insertion gain. For each of three subject groups, 12 in-the-ear style hearing aids with Class D circuitry and similar dispenser controls were ordered from one of three manufacturers. Subject groups were classified based on the type of information included on the hearing aid order form: (1) the subject's audiogram, (2) a three-part matrix specifying the desired maximum output, full-on gain, and frequency response slope of the hearing aid, or (3) the desired 2-cc coupler full-in grain of the hearing aid, based on real-ear coupler difference (RECD) measurements. Following electroacoustic adjustments aimed at approximating a commonly used target insertion gain formula, results revealed no significant differences among any of the three selection procedures with respect to obtaining acceptable insertion gain values.

  19. Rapid and targeted introgression of genes into popular wheat cultivars using marker-assisted background selection.

    Directory of Open Access Journals (Sweden)

    Harpinder S Randhawa

    Full Text Available A marker-assisted background selection (MABS-based gene introgression approach in wheat (Triticum aestivum L. was optimized, where 97% or more of a recurrent parent genome (RPG can be recovered in just two backcross (BC generations. A four-step MABS method was developed based on 'Plabsim' computer simulations and wheat genome structure information. During empirical optimization of this method, double recombinants around the target gene were selected in a step-wise fashion during the two BC cycles followed by selection for recurrent parent genotype on non-carrier chromosomes. The average spacing between carrier chromosome markers was <4 cM. For non-carrier chromosome markers that flanked each of the 48 wheat gene-rich regions, this distance was approximately 12 cM. Employed to introgress seedling stripe rust (Puccinia striiformis f. sp. tritici resistance gene Yr15 into the spring wheat cultivar 'Zak', marker analysis of 2,187 backcross-derived progeny resulted in the recovery of a BC(2F(2ratio3 plant with 97% of the recurrent parent genome. In contrast, only 82% of the recurrent parent genome was recovered in phenotypically selected BC(4F(7 plants developed without MABS. Field evaluation results from 17 locations indicated that the MABS-derived line was either equal or superior to the recurrent parent for the tested agronomic characteristics. Based on these results, MABS is recommended as a strategy for rapidly introgressing a targeted gene into a wheat genotype in just two backcross generations while recovering 97% or more of the recurrent parent genotype.

  20. Evodiamine selectively targets cancer stem-like cells through the p53-p21-Rb pathway

    International Nuclear Information System (INIS)

    Han, Seula; Woo, Jong Kyu; Jung, Yuchae; Jeong, Dawoon; Kang, Minsook; Yoo, Young-Ji; Lee, Hani; Oh, Seung Hyun; Ryu, Jae-Ha; Kim, Woo-Young

    2016-01-01

    In spite of the recent improvements, the resistance to chemotherapy/radiotherapy followed by relapse is the main hurdle for the successful treatment of breast cancer, a leading cause of death in women. A small population of breast cancer cells that have stem-like characteristics (cancer stem-like cells; CSLC) may contribute to this resistance and relapse. Here, we report on a component of a traditional Chinese medicine, evodiamine, which selectively targets CSLC of breast cancer cell lines MCF7 and MDAMB 231 at a concentration that does show a little or no cytotoxic effect on bulk cancer cells. While evodiamine caused the accumulation of bulk cancer cells at the G2/M phase, it did not hold CSLC in a specific cell cycle phase but instead, selectively killed CSLC. This was not due to the culture of CSLC in suspension or without FBS. A proteomic analysis and western blotting revealed that evodiamine changed the expression of cell cycle regulating molecules more efficiently in CSLC cells than in bulk cancer cells. Surprisingly, evodiamine selectively activated p53 and p21 and decreased inactive Rb, the master molecules in G1/S checkpoint. These data collectively suggest a novel mechanism involving CSLC-specific targeting by evodiamine and its possible use to the therapy of breast cancer. - Highlights: • Evodiamine selectively kills breast cancer stem like cells at G1 phase. • Evodiamine utilizes different mechanism of cell cycle modulation in CSLC and in bulk cancer cells. • Evodiamine activate the p53, p21 and Rb pathway.

  1. Evodiamine selectively targets cancer stem-like cells through the p53-p21-Rb pathway

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seula [The Research Center for Cell Fate Control, College of Pharmacy, Sookmyung Women' s University, Seoul (Korea, Republic of); Woo, Jong Kyu [College of Pharmacy, Gachon University, Incheon (Korea, Republic of); Jung, Yuchae; Jeong, Dawoon; Kang, Minsook; Yoo, Young-Ji; Lee, Hani [The Research Center for Cell Fate Control, College of Pharmacy, Sookmyung Women' s University, Seoul (Korea, Republic of); Oh, Seung Hyun [College of Pharmacy, Gachon University, Incheon (Korea, Republic of); Ryu, Jae-Ha [The Research Center for Cell Fate Control, College of Pharmacy, Sookmyung Women' s University, Seoul (Korea, Republic of); Kim, Woo-Young, E-mail: wykim@sookmyung.ac.kr [The Research Center for Cell Fate Control, College of Pharmacy, Sookmyung Women' s University, Seoul (Korea, Republic of)

    2016-01-22

    In spite of the recent improvements, the resistance to chemotherapy/radiotherapy followed by relapse is the main hurdle for the successful treatment of breast cancer, a leading cause of death in women. A small population of breast cancer cells that have stem-like characteristics (cancer stem-like cells; CSLC) may contribute to this resistance and relapse. Here, we report on a component of a traditional Chinese medicine, evodiamine, which selectively targets CSLC of breast cancer cell lines MCF7 and MDAMB 231 at a concentration that does show a little or no cytotoxic effect on bulk cancer cells. While evodiamine caused the accumulation of bulk cancer cells at the G2/M phase, it did not hold CSLC in a specific cell cycle phase but instead, selectively killed CSLC. This was not due to the culture of CSLC in suspension or without FBS. A proteomic analysis and western blotting revealed that evodiamine changed the expression of cell cycle regulating molecules more efficiently in CSLC cells than in bulk cancer cells. Surprisingly, evodiamine selectively activated p53 and p21 and decreased inactive Rb, the master molecules in G1/S checkpoint. These data collectively suggest a novel mechanism involving CSLC-specific targeting by evodiamine and its possible use to the therapy of breast cancer. - Highlights: • Evodiamine selectively kills breast cancer stem like cells at G1 phase. • Evodiamine utilizes different mechanism of cell cycle modulation in CSLC and in bulk cancer cells. • Evodiamine activate the p53, p21 and Rb pathway.

  2. A QUASAR CATALOG WITH SIMULTANEOUS UV, OPTICAL, AND X-RAY OBSERVATIONS BY SWIFT

    Energy Technology Data Exchange (ETDEWEB)

    Wu Jian; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P.; Gronwall, Caryl; Porterfield, Blair L. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Vanden Berk, Daniel; Wesolowski, Sarah, E-mail: jwu@astro.psu.edu [Department of Physics, Saint Vincent College, 300 Fraser Purchase Road, Latrobe, PA 15650 (United States)

    2012-08-01

    We have compiled a catalog of optically selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma-ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both Ultraviolet Optical Telescope (UVOT) and X-Ray Telescope (XRT) observations and 354 of which are detected by both instruments. The overall X-ray detection rate is {approx}60% which rises to {approx}85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution (SED) for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about {approx}0.3 dex to the quasar luminosity. We re-visit the {alpha}{sub ox}-L{sub 2500A} relation by selecting a clean sample with only Type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared with studies that use non-simultaneous UV/optical and X-ray data. We only found a weak correlation between L{sub bol}/L{sub Edd} and {alpha}{sub UV}. We do not find significant correlations between {alpha}{sub x} and {alpha}{sub ox}, {alpha}{sub ox} and {alpha}{sub UV}, and {alpha}{sub x} and log L(0.3-10 keV). The correlations between {alpha}{sub UV} and {alpha}{sub x}, {alpha}{sub ox} and {alpha}{sub x}, {alpha}{sub ox} and {alpha}{sub UV}, L{sub bol}/L{sub Edd} and {alpha}{sub x}, and L{sub bol}/L{sub Edd} and {alpha}{sub ox} are stronger among low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state.

  3. A time dependent search for neutrino emission from micro-quasars with the ANTARES telescope

    International Nuclear Information System (INIS)

    Galata, S.

    2012-01-01

    The ANTARES collaboration has successfully built, deployed and is currently operating an underwater Cherenkov detector dedicated to high energy neutrino astronomy. The primary aim of the experiment is to detect cosmic sources of neutrinos in order to reveal the production sites of cosmic rays. Among the sources likely to be significant sources of neutrinos are those accelerating relativistic jets, like gamma ray bursts, active galactic nuclei and micro-quasars. Micro-quasars are binary systems formed by a compact object accreting mass from a companion star. The mass transfer causes the emission of X-rays, whereas the onset of magnetic forces in the accreting plasma can cause the acceleration of relativistic jets, which are observed by radio telescopes via their non-thermal synchrotron emission. In some systems, a correlation between X-ray and radio light curves indicates an interplay between accretion and ejection respectively. Some micro-quasars are also high energy and very high energy gamma ray emitters. In this thesis, a time dependent search for neutrino emission from micro-quasars was performed with a multi-messenger approach (photon/neutrino). The data from the X-ray monitors RXTE/ASM and SWIFT/BAT, and the gamma-ray telescope FERMI/LAT were used to select transient events in which the source was supposed to accelerate relativistic jets. The restriction of the analysis to the ejection periods allows a drastic reduction of atmospheric muon and neutrino background, and thus to increase the chances of a discovery. The search was performed with the ANTARES data taken between 2007 and 2010. Statistical analysis was carried out using an un-binned likelihood method based on a likelihood ratio test. The cuts for the event selection were optimized in order to maximize the chance of a discovery. As no neutrino signal was observed in correlation with these micro-quasars, upper limits on the neutrino fluxes of the micro-quasars under study were calculated and compared

  4. Criteria for selection of target materials and design of high-efficiency-release targets for radioactive ion beam generation

    CERN Document Server

    Alton, G D; Liu, Y

    1999-01-01

    In this report, we define criteria for choosing target materials and for designing, mechanically stable, short-diffusion-length, highly permeable targets for generation of high-intensity radioactive ion beams (RIBs) for use at nuclear physics and astrophysics research facilities based on the ISOL principle. In addition, lists of refractory target materials are provided and examples are given of a number of successful targets, based on these criteria, that have been fabricated and tested for use at the Holifield Radioactive Ion Beam Facility (HRIBF).

  5. The selective processing of emotional visual stimuli while detecting auditory targets: an ERP analysis.

    Science.gov (United States)

    Schupp, Harald T; Stockburger, Jessica; Bublatzky, Florian; Junghöfer, Markus; Weike, Almut I; Hamm, Alfons O

    2008-09-16

    Event-related potential studies revealed an early posterior negativity (EPN) for emotional compared to neutral pictures. Exploring the emotion-attention relationship, a previous study observed that a primary visual discrimination task interfered with the emotional modulation of the EPN component. To specify the locus of interference, the present study assessed the fate of selective visual emotion processing while attention is directed towards the auditory modality. While simply viewing a rapid and continuous stream of pleasant, neutral, and unpleasant pictures in one experimental condition, processing demands of a concurrent auditory target discrimination task were systematically varied in three further experimental conditions. Participants successfully performed the auditory task as revealed by behavioral performance and selected event-related potential components. Replicating previous results, emotional pictures were associated with a larger posterior negativity compared to neutral pictures. Of main interest, increasing demands of the auditory task did not modulate the selective processing of emotional visual stimuli. With regard to the locus of interference, selective emotion processing as indexed by the EPN does not seem to reflect shared processing resources of visual and auditory modality.

  6. Selective Targeting of SH2 Domain–Phosphotyrosine Interactions of Src Family Tyrosine Kinases with Monobodies

    Energy Technology Data Exchange (ETDEWEB)

    Kükenshöner, Tim; Schmit, Nadine Eliane; Bouda, Emilie; Sha, Fern; Pojer, Florence; Koide, Akiko; Seeliger, Markus; Koide, Shohei; Hantschel, Oliver

    2017-05-01

    The binding of Src-homology 2 (SH2) domains to phosphotyrosine (pY) sites is critical for the autoinhibition and substrate recognition of the eight Src family kinases (SFKs). The high sequence conservation of the 120 human SH2 domains poses a significant challenge to selectively perturb the interactions of even the SFK SH2 family against the rest of the SH2 domains. We have developed synthetic binding proteins, termed monobodies, for six of the SFK SH2 domains with nanomolar affinity. Most of these monobodies competed with pY ligand binding and showed strong selectivity for either the SrcA (Yes, Src, Fyn, Fgr) or SrcB subgroup (Lck, Lyn, Blk, Hck). Interactome analysis of intracellularly expressed monobodies revealed that they bind SFKs but no other SH2-containing proteins. Three crystal structures of monobody–SH2 complexes unveiled different and only partly overlapping binding modes, which rationalized the observed selectivity and enabled structure-based mutagenesis to modulate inhibition mode and selectivity. In line with the critical roles of SFK SH2 domains in kinase autoinhibition and T-cell receptor signaling, monobodies binding the Src and Hck SH2 domains selectively activated respective recombinant kinases, whereas an Lck SH2-binding monobody inhibited proximal signaling events downstream of the T-cell receptor complex. Our results show that SFK SH2 domains can be targeted with unprecedented potency and selectivity using monobodies. They are excellent tools for dissecting SFK functions in normal development and signaling and to interfere with aberrant SFK signaling networks in cancer cells.

  7. Selective Targeting of SH2 Domain-Phosphotyrosine Interactions of Src Family Tyrosine Kinases with Monobodies.

    Science.gov (United States)

    Kükenshöner, Tim; Schmit, Nadine Eliane; Bouda, Emilie; Sha, Fern; Pojer, Florence; Koide, Akiko; Seeliger, Markus; Koide, Shohei; Hantschel, Oliver

    2017-05-05

    The binding of Src-homology 2 (SH2) domains to phosphotyrosine (pY) sites is critical for the autoinhibition and substrate recognition of the eight Src family kinases (SFKs). The high sequence conservation of the 120 human SH2 domains poses a significant challenge to selectively perturb the interactions of even the SFK SH2 family against the rest of the SH2 domains. We have developed synthetic binding proteins, termed monobodies, for six of the SFK SH2 domains with nanomolar affinity. Most of these monobodies competed with pY ligand binding and showed strong selectivity for either the SrcA (Yes, Src, Fyn, Fgr) or SrcB subgroup (Lck, Lyn, Blk, Hck). Interactome analysis of intracellularly expressed monobodies revealed that they bind SFKs but no other SH2-containing proteins. Three crystal structures of monobody-SH2 complexes unveiled different and only partly overlapping binding modes, which rationalized the observed selectivity and enabled structure-based mutagenesis to modulate inhibition mode and selectivity. In line with the critical roles of SFK SH2 domains in kinase autoinhibition and T-cell receptor signaling, monobodies binding the Src and Hck SH2 domains selectively activated respective recombinant kinases, whereas an Lck SH2-binding monobody inhibited proximal signaling events downstream of the T-cell receptor complex. Our results show that SFK SH2 domains can be targeted with unprecedented potency and selectivity using monobodies. They are excellent tools for dissecting SFK functions in normal development and signaling and to interfere with aberrant SFK signaling networks in cancer cells. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  8. Quasar evolution: not a deficit at low redshifts

    International Nuclear Information System (INIS)

    Avni, Y.; Schiller, N.

    1983-01-01

    We consider the recent suggestion of Hawkins and Stewart that complete quasar samples can be interpreted in terms of a (real or apparent) deficit of quasars at low redshifts. By using a larger sample and a more efficient method of analysis, we rule out this interpretation

  9. X-ray, optical, and radio properties of quasars

    International Nuclear Information System (INIS)

    Blumenthal, G.R.; Keel, W.C.; Miller, J.S.

    1982-01-01

    We have examined a sample of 26 low-redshift quasars for the relationships between X-ray luminosity and optical spectroscopic features. All quasars were observed with the Einstein Observatory and with the IDS on the Lick 3 meter telescope. We find evidence for correlations between quasar X-ray luminosity and both optical continuum luminosity and Hβ luminosity. In the latter case, there is a smooth relationship connecting quasars, Seyfert 1, and Seyfert 2 galaxies. For the quasars in this sample, there is also a strong correlation between optical continuum luminosity and both the Hβ luminosity and equivalent width. Unlike the case for Seyfert 1 nuclei, there is no evidence for a correlation between X-ray luminosity and either the Hβ/[O III] ratio or the width at zero intensity of the Hβ line. However, we do find some evidence for a weak correlation between α'/sub o/x, the mean continuum spectral index between 5000 A and 2 keV, and Fe II equivalent width, Hβ equivalent width, Hβ line width at zero intensity, and the ratio of Hβ equivalent width to its line width at zero intensity. Overall, we found few strong correlations between optical spectroscopic quanitites and X-ray properties of quasars. Some of the implications of these results for models of quasars and quasar emission line regions are discussed

  10. Clues to quasar broad-line region geometry and kinematics

    NARCIS (Netherlands)

    Vestergaard, M; Wilkes, BJ; Barthel, PD

    2000-01-01

    We present evidence that the high-velocity C IV lambda 1549 emission-line gas of radio-loud quasars may originate in a disklike configuration, in close proximity to the accretion disk often assumed to emit the low-ionization lines. For a sample of 36 radio-loud z approximate to 2 quasars, we find

  11. Statistical studies on quasars and active nuclei of galaxies

    International Nuclear Information System (INIS)

    Stasinska, G.

    1987-01-01

    A catalogue of optical, radio and X-ray properties of quasars and other active galactic nuclei, now in elaboration, is presented. This catalogue may serve as a data base for statistical studies. As an example, we give some preliminary results concerning the determination of the quasar masses [fr

  12. High-redshift SDSS Quasars with Weak Emission Lines

    DEFF Research Database (Denmark)

    Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Brandt, W. N.

    2009-01-01

    We identify a sample of 74 high-redshift quasars (z > 3) with weak emission lines from the Fifth Data Release of the Sloan Digital Sky Survey and present infrared, optical, and radio observations of a subsample of four objects at z > 4. These weak emission-line quasars (WLQs) constitute a promine...

  13. THE FIRST HIGH-REDSHIFT QUASAR FROM Pan-STARRS

    International Nuclear Information System (INIS)

    Morganson, Eric; De Rosa, Gisella; Decarli, Roberto; Walter, Fabian; Rix, Hans-Walter; Chambers, Ken; Burgett, William; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nick; Magnier, Eugene; Sweeney, Bill; Waters, Christopher; McGreer, Ian; Fan, Xiaohui; Greiner, Jochen; Price, Paul

    2012-01-01

    We present the discovery of the first high-redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i P1 dropout in PS1, confirmed photometrically with the SAO Wide-field InfraRed Camera at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph at the Calar Alto 3.5 m telescope. Its near-infrared spectrum was taken at the Large Binocular Telescope Observatory (LBT) with the LBT Near-Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research. It has a redshift of 5.73, an AB z P1 magnitude of 19.4, a luminosity of 3.8 × 10 47 erg s –1 , and a black hole mass of 6.9 × 10 9 M ☉ . It is a broad absorption line quasar with a prominent Lyβ peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high-redshift quasar search that is projected to discover more than 100 i P1 dropout quasars and could potentially find more than 10 z P1 dropout (z > 6.8) quasars.

  14. Close Companions to Two High-redshift Quasars

    Science.gov (United States)

    McGreer, Ian D.; Fan, Xiaohui; Strauss, Michael A.; Haiman, Zoltàn; Richards, Gordon T.; Jiang, Linhua; Bian, Fuyan; Schneider, Donald P.

    2014-10-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i AB = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW0 ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ~ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ~4.5 mag fainter than the quasar (Y AB = 25) at a separation of 0.''9. The red i 775 - Y 105 color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs #12184 and #12493. Observations were also made with the LBT and MMT.

  15. Sejong Open Cluster Survey (SOS). 0. Target Selection and Data Analysis

    Science.gov (United States)

    Sung, Hwankyung; Lim, Beomdu; Bessell, Michael S.; Kim, Jinyoung S.; Hur, Hyeonoh; Chun, Moo-Young; Park, Byeong-Gon

    2013-06-01

    Star clusters are superb astrophysical laboratories containing cospatial and coeval samples of stars with similar chemical composition. We initiate the Sejong Open cluster Survey (SOS) - a project dedicated to providing homogeneous photometry of a large number of open clusters in the SAAO Johnson-Cousins' UBVI system. To achieve our main goal, we pay much attention to the observation of standard stars in order to reproduce the SAAO standard system. Many of our targets are relatively small sparse clusters that escaped previous observations. As clusters are considered building blocks of the Galactic disk, their physical properties such as the initial mass function, the pattern of mass segregation, etc. give valuable information on the formation and evolution of the Galactic disk. The spatial distribution of young open clusters will be used to revise the local spiral arm structure of the Galaxy. In addition, the homogeneous data can also be used to test stellar evolutionary theory, especially concerning rare massive stars. In this paper we present the target selection criteria, the observational strategy for accurate photometry, and the adopted calibrations for data analysis such as color-color relations, zero-age main sequence relations, Sp - M_V relations, Sp - T_{eff} relations, Sp - color relations, and T_{eff} - BC relations. Finally we provide some data analysis such as the determination of the reddening law, the membership selection criteria, and distance determination.

  16. Advancing the sensitivity of selected reaction monitoring-based targeted quantitative proteomics

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Tujin; Su, Dian; Liu, Tao; Tang, Keqi; Camp, David G.; Qian, Weijun; Smith, Richard D.

    2012-04-01

    Selected reaction monitoring (SRM)—also known as multiple reaction monitoring (MRM)—has emerged as a promising high-throughput targeted protein quantification technology for candidate biomarker verification and systems biology applications. A major bottleneck for current SRM technology, however, is insufficient sensitivity for e.g., detecting low-abundance biomarkers likely present at the pg/mL to low ng/mL range in human blood plasma or serum, or extremely low-abundance signaling proteins in the cells or tissues. Herein we review recent advances in methods and technologies, including front-end immunoaffinity depletion, fractionation, selective enrichment of target proteins/peptides or their posttranslational modifications (PTMs), as well as advances in MS instrumentation, which have significantly enhanced the overall sensitivity of SRM assays and enabled the detection of low-abundance proteins at low to sub- ng/mL level in human blood plasma or serum. General perspectives on the potential of achieving sufficient sensitivity for detection of pg/mL level proteins in plasma are also discussed.

  17. Does Angling Technique Selectively Target Fishes Based on Their Behavioural Type?

    Directory of Open Access Journals (Sweden)

    Alexander D M Wilson

    Full Text Available Recently, there has been growing recognition that fish harvesting practices can have important impacts on the phenotypic distributions and diversity of natural populations through a phenomenon known as fisheries-induced evolution. Here we experimentally show that two common recreational angling techniques (active crank baits versus passive soft plastics differentially target wild largemouth bass (Micropterus salmoides and rock bass (Ambloplites rupestris based on variation in their behavioural tendencies. Fish were first angled in the wild using both techniques and then brought back to the laboratory and tested for individual-level differences in common estimates of personality (refuge emergence, flight-initiation-distance, latency-to-recapture and with a net, and general activity in an in-lake experimental arena. We found that different angling techniques appear to selectively target these species based on their boldness (as characterized by refuge emergence, a standard measure of boldness in fishes but not other assays of personality. We also observed that body size was independently a significant predictor of personality in both species, though this varied between traits and species. Our results suggest a context-dependency for vulnerability to capture relative to behaviour in these fish species. Ascertaining the selective pressures angling practices exert on natural populations is an important area of fisheries research with significant implications for ecology, evolution, and resource management.

  18. Target objects defined by a conjunction of colour and shape can be selected independently and in parallel.

    Science.gov (United States)

    Jenkins, Michael; Grubert, Anna; Eimer, Martin

    2017-11-01

    It is generally assumed that during search for targets defined by a feature conjunction, attention is allocated sequentially to individual objects. We tested this hypothesis by tracking the time course of attentional processing biases with the N2pc component in tasks where observers searched for two targets defined by a colour/shape conjunction. In Experiment 1, two displays presented in rapid succession (100 ms or 10 ms SOA) each contained a target and a colour-matching or shape-matching distractor on opposite sides. Target objects in both displays elicited N2pc components of similar size that overlapped in time when the SOA was 10 ms, suggesting that attention was allocated in parallel to both targets. Analogous results were found in Experiment 2, where targets and partially matching distractors were both accompanied by an object without target-matching features. Colour-matching and shape-matching distractors also elicited N2pc components, and the target N2pc was initially identical to the sum of the two distractor N2pcs, suggesting that the initial phase of attentional object selection was guided independently by feature templates for target colour and shape. Beyond 230 ms after display onset, the target N2pc became superadditive, indicating that attentional selection processes now started to be sensitive to the presence of feature conjunctions. Results show that independent attentional selection processes can be activated in parallel by two target objects in situations where these objects are defined by a feature conjunction.

  19. The clustering of quasars from an objective-prism survey

    International Nuclear Information System (INIS)

    Webster, A.

    1982-01-01

    The positions and redshifts of 108 quasars from the Cerro Tololo objective-prism survey are subjected to Fourier Power Spectrum Analysis in a search for clustering in their spatial distribution. It is found that, on the whole, these quasars are not clustered but are scattered in space independently at random. The sole exception is a group of four quasars at z = 0.37 which has a low probability of being a chance event and which, with a size of about 100 Mpc, may therefore be the largest known structure in the Universe. The conclusions disagree with Arp's analysis of this catalogue: his 'clouds of quasars' ejected by certain low-redshift galaxies, for example, are attributable to sensitivity variations among the different plates of the survey. It is shown that analysis of deeper surveys is likely to show up quasar clusters even at high redshift, and could therefore provide a useful new cosmological probe. (author)

  20. The LAMOST survey of background quasars in the vicinity of the Andromeda and Triangulum galaxies. II. Results from the commissioning observations and the pilot surveys

    International Nuclear Information System (INIS)

    Huo, Zhi-Ying; Bai, Zhong-Rui; Chen, Jian-Jun; Chen, Xiao-Yan; Du, Bing; Jia, Lei; Lei, Ya-Juan; Liu, Xiao-Wei; Yuan, Hai-Bo; Xiang, Mao-Sheng; Huang, Yang; Zhang, Hui-Hua; Yan, Lin; Chu, Jia-Ru; Chu, Yao-Quan; Hu, Hong-Zhuan; Cui, Xiang-Qun; Hou, Yong-Hui; Hu, Zhong-Wen; Jiang, Fang-Hua

    2013-01-01

    We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named the Guoshoujing Telescope, during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey, Kitt Peak National Observatory 4 m telescope, Xuyi Schmidt Telescope Photometric Survey optical, and Wide-field Infrared Survey Explorer near-infrared photometric data. We present 509 new quasars discovered in a stripe of ∼135 deg 2 from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey data sets, and also 17 new quasars discovered in an area of ∼100 deg 2 that covers the central region and the southeastern halo of M31 in the 2010 commissioning data sets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62, and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5, and 18.0, respectively, of which 5, 20, and 75 are newly discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the interstellar/intergalactic medium in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.°5 of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds are behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute proper motions (PMs) of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local Group.

  1. Selective synaptic targeting of the excitatory and inhibitory presynaptic organizers FGF22 and FGF7.

    Science.gov (United States)

    Terauchi, Akiko; Timmons, Kendall M; Kikuma, Koto; Pechmann, Yvonne; Kneussel, Matthias; Umemori, Hisashi

    2015-01-15

    Specific formation of excitatory and inhibitory synapses is crucial for proper functioning of the brain. Fibroblast growth factor 22 (FGF22) and FGF7 are postsynaptic-cell-derived presynaptic organizers necessary for excitatory and inhibitory presynaptic differentiation, respectively, in the hippocampus. For the establishment of specific synaptic networks, these FGFs must localize to appropriate synaptic locations - FGF22 to excitatory and FGF7 to inhibitory postsynaptic sites. Here, we show that distinct motor and adaptor proteins contribute to intracellular microtubule transport of FGF22 and FGF7. Excitatory synaptic targeting of FGF22 requires the motor proteins KIF3A and KIF17 and the adaptor protein SAP102 (also known as DLG3). By contrast, inhibitory synaptic targeting of FGF7 requires the motor KIF5 and the adaptor gephyrin. Time-lapse imaging shows that FGF22 moves with SAP102, whereas FGF7 moves with gephyrin. These results reveal the basis of selective targeting of the excitatory and inhibitory presynaptic organizers that supports their different synaptogenic functions. Finally, we found that knockdown of SAP102 or PSD95 (also known as DLG4), which impairs the differentiation of excitatory synapses, alters FGF7 localization, suggesting that signals from excitatory synapses might regulate inhibitory synapse formation by controlling the distribution of the inhibitory presynaptic organizer. © 2015. Published by The Company of Biologists Ltd.

  2. Scientific objectives and selection of targets for the SMART-1 Infrared Spectrometer (SIR)

    Science.gov (United States)

    Basilevsky, A. T.; Keller, H. U.; Nathues, A.; Mall, U.; Hiesinger, H.; Rosiek, M.

    2004-12-01

    The European SMART-1 mission to the Moon, primarily a testbed for innovative technologies, was launched in September 2003 and will reach the Moon in 2005. On board are several scientific instruments, including the point-spectrometer SMART-1 Infrared Spectrometer (SIR). Taking into account the capabilities of the SMART-1 mission and the SIR instrument in particular, as well as the open questions in lunar science, a selection of targets for SIR observations has been compiled. SIR can address at least five topics: (1) Surface/regolith processes; (2) Lunar volcanism; (3) Lunar crust structure; (4) Search for spectral signatures of ices at the lunar poles; and (5) Ground truth and study of geometric effects on the spectral shape. For each topic we will discuss specific observation modes, necessary to achieve our scientific goals. The majority of SIR targets will be observed in the nadir-tracking mode. More than 100 targets, which require off-nadir pointing and off-nadir tracking, are planned. It is expected that results of SIR observations will significantly increase our understanding of the Moon. Since the exact arrival date and the orbital parameters of the SMART-1 spacecraft are not known yet, a more detailed planning of the scientific observations will follow in the near future.

  3. Selection of flowing liquid lead target structural materials for accelerator driven transmutation applications

    International Nuclear Information System (INIS)

    Park, J.J.; Buksa, J.J.

    1994-01-01

    The beam entry window and container for a liquid lead spallation target will be exposed to high fluxes of protons and neutrons that are both higher in magnitude and energy than have been experienced in proton accelerators and fission reactors, as well as in a corrosive environment. The structural material of the target should have a good compatibility with liquid lead, a sufficient mechanical strength at elevated temperatures, a good performance under an intense irradiation environment, and a low neutron absorption cross section; these factors have been used to rank the applicability of a wide range of materials for structural containment Nb-1Zr has been selected for use as the structural container for the LANL ABC/ATW molten lead target. Corrosion and mass transfer behavior for various candidate structural materials in liquid lead are reviewed, together with the beneficial effects of inhibitors and various coatings to protect substrate against liquid lead corrosion. Mechanical properties of some candidate materials at elevated temperatures and the property changes resulting from 800 MeV proton irradiation are also reviewed

  4. HisB as novel selection marker for gene targeting approaches in Aspergillus niger.

    Science.gov (United States)

    Fiedler, Markus R M; Gensheimer, Tarek; Kubisch, Christin; Meyer, Vera

    2017-03-08

    For Aspergillus niger, a broad set of auxotrophic and dominant resistance markers is available. However, only few offer targeted modification of a gene of interest into or at a genomic locus of choice, which hampers functional genomics studies. We thus aimed to extend the available set by generating a histidine auxotrophic strain with a characterized hisB locus for targeted gene integration and deletion in A. niger. A histidine-auxotrophic strain was established via disruption of the A. niger hisB gene by using the counterselectable pyrG marker. After curing, a hisB - , pyrG - strain was obtained, which served as recipient strain for further studies. We show here that both hisB orthologs from A. nidulans and A. niger can be used to reestablish histidine prototrophy in this recipient strain. Whereas the hisB gene from A. nidulans was suitable for efficient gene targeting at different loci in A. niger, the hisB gene from A. niger allowed efficient integration of a Tet-on driven luciferase reporter construct at the endogenous non-functional hisB locus. Subsequent analysis of the luciferase activity revealed that the hisB locus is tight under non-inducing conditions and allows even higher luciferase expression levels compared to the pyrG integration locus. Taken together, we provide here an alternative selection marker for A. niger, hisB, which allows efficient homologous integration rates as well as high expression levels which compare favorably to the well-established pyrG selection marker.

  5. NuSTAR unveils a compton-thick 2 quasar in MrK 34

    DEFF Research Database (Denmark)

    Gandhi, P.; Lansbury, G. B.; Alexander, D. M.

    2014-01-01

    We present Nuclear Spectroscopic Telescope Array (NuSTAR) 3-40 keV observations of the optically selected Type 2 quasar (QSO2) SDSS J1034+6001 or Mrk 34. The high-quality hard X-ray spectrum and archival XMM-Newton data can be fitted self-consistently with a reflection-dominated continuum...... standard" CT QSO2 and is the nearest non-merging system in this class, in contrast to the other local CT quasar NGC 6240, which is currently undergoing a major merger coupled with strong star formation. For typical X-ray bolometric correction factors, the accretion luminosity of Mrk 34 is high enough...... to potentially power the total infrared luminosity. X-ray spectral fitting also shows that thermal emission related to star formation is unlikely to drive the observed bright soft component below similar to 3 keV, favoring photoionization instead....

  6. A Full Year's Chandra Exposure on Sloan Digital Sky Survey Quasars from the Chandra Multiwavelength Project

    Science.gov (United States)

    Green, Paul J.; Aldcroft, T. L.; Richards, G. T.; Barkhouse, W. A.; Constantin, A.; Haggard, D.; Karovska, M.; Kim, D.-W.; Kim, M.; Vikhlinin, A.; Anderson, S. F.; Mossman, A.; Kashyap, V.; Myers, A. D.; Silverman, J. D.; Wilkes, B. J.; Tananbaum, H.

    2009-01-01

    We study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project. Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.2 3, substantially expanding the known sample. We find no evidence for evolution out to z ~ 5 for either the X-ray photon index Γ or for the ratio of optical/UV to X-ray flux αox. About 10% of detected QSOs show best-fit intrinsic absorbing columns greater than 1022 cm-2, but the fraction might reach ~1/3 if most nondetections are absorbed. We confirm a significant correlation between αox and optical luminosity, but it flattens or disappears for fainter (MB gsim -23) active galactic nucleus (AGN) alone. We report significant hardening of Γ both toward higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in nonthermal X-ray emission, and our findings thereby strengthen analogies between Galactic black hole binaries and AGN. For uniformly selected subsamples of narrow-line Seyfert 1s and narrow absorption line QSOs, we find no evidence for unusual distributions of either αox or Γ.

  7. Selective Vitamin D Receptor Activation as Anti-Inflammatory Target in Chronic Kidney Disease

    Directory of Open Access Journals (Sweden)

    J. Donate-Correa

    2014-01-01

    Full Text Available Paricalcitol, a selective vitamin D receptor (VDR activator used for treatment of secondary hyperparathyroidism in chronic kidney disease (CKD, has been associated with survival advantages, suggesting that this drug, beyond its ability to suppress parathyroid hormone, may have additional beneficial actions. In this prospective, nonrandomised, open-label, proof-of-concept study, we evaluated the hypothesis that selective vitamin D receptor activation with paricalcitol is an effective target to modulate inflammation in CKD patients. Eight patients with an estimated glomerular filtration rate between 15 and 44 mL/min/1.73 m2 and an intact parathyroid hormone (PTH level higher than 110 pg/mL received oral paricalcitol (1 μg/48 hours as therapy for secondary hyperparathyroidism. Nine patients matched by age, sex, and stage of CKD, but a PTH level <110 pg/mL, were enrolled as a control group. Our results show that five months of paricalcitol administration were associated with a reduction in serum concentrations of hs-CRP (13.9%, P<0.01, TNF-α (11.9%, P=0.01, and IL-6 (7%, P<0.05, with a nonsignificant increase of IL-10 by 16%. In addition, mRNA expression levels of the TNFα and IL-6 genes in peripheral blood mononuclear cells decreased significantly by 30.8% (P=0.01 and 35.4% (P=0.01, respectively. In conclusion, selective VDR activation is an effective target to modulate inflammation in CKD.

  8. In quest of axionic hairs in quasars

    Science.gov (United States)

    Banerjee, Indrani; Mandal, Bhaswati; SenGupta, Soumitra

    2018-03-01

    The presence of axionic field can provide plausible explanation to several long standing problems in physics such as dark matter and dark energy. The pseudo-scalar axion whose derivative corresponds to the Hodge dual of the Kalb-Ramond field strength in four dimensions plays crucial roles in explaining several astrophysical and cosmological observations. Therefore, the detection of axionic hairs/Kalb-Ramond field which appears as closed string excitations in the heterotic string spectrum may provide a profound insight to our understanding of the current universe. The current level of precision achieved in solar-system based tests employed to test general relativity, is not sufficient to detect the presence of axion. However, the near horizon regime of quasars where the curvature effects are maximum seems to be a natural laboratory to probe such additions to the matter sector. The continuum spectrum emitted from the accretion disk around quasars encapsulates the imprints of the background spacetime and hence acts as a storehouse of information regarding the nature of gravitational interaction in extreme situations. The surfeit of data available in the electromagnetic domain provides a further motivation to explore such systems. Using the optical data for eighty Palomar Green quasars we demonstrate that the theoretical estimates of optical luminosity explain the observations best when the axionic field is assumed to be absent. However, axion which violates the energy condition seems to be favored by observations which has several interesting consequences. Error estimators, including reduced χ2, Nash-Sutcliffe efficiency, index of agreement and modified versions of the last two are used to solidify our conclusion and the implications of our result are discussed.

  9. High redshift quasars and high metallicities

    Science.gov (United States)

    Ferland, Gary J.

    1997-01-01

    A large-scale code called Cloudy was designed to simulate non-equilibrium plasmas and predict their spectra. The goal was to apply it to studies of galactic and extragalactic emission line objects in order to reliably deduce abundances and luminosities. Quasars are of particular interest because they are the most luminous objects in the universe and the highest redshift objects that can be observed spectroscopically, and their emission lines can reveal the composition of the interstellar medium (ISM) of the universe when it was well under a billion years old. The lines are produced by warm (approximately 10(sup 4)K) gas with moderate to low density (n less than or equal to 10(sup 12) cm(sup -3)). Cloudy has been extended to include approximately 10(sup 4) resonance lines from the 495 possible stages of ionization of the lightest 30 elements, an extension that required several steps. The charge transfer database was expanded to complete the needed reactions between hydrogen and the first four ions and fit all reactions with a common approximation. Radiative recombination rate coefficients were derived for recombination from all closed shells, where this process should dominate. Analytical fits to Opacity Project (OP) and other recent photoionization cross sections were produced. Finally, rescaled OP oscillator strengths were used to compile a complete set of data for 5971 resonance lines. The major discovery has been that high redshift quasars have very high metallicities and there is strong evidence that the quasar phenomenon is associated with the birth of massive elliptical galaxies.

  10. Optical images of quasars and radio galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hutchings, J.B.; Johnson, I.; Pyke, R.

    1988-04-01

    Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions. 12 references.

  11. Optical images of quasars and radio galaxies

    International Nuclear Information System (INIS)

    Hutchings, J.B.; Johnson, I.; Pyke, R.

    1988-01-01

    Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions. 12 references

  12. Optical images of quasars and radio galaxies

    Science.gov (United States)

    Hutchings, J. B.; Johnson, I.; Pyke, R.

    1988-04-01

    Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions.

  13. Novel Chemokine-Based Immunotoxins for Potent and Selective Targeting of Cytomegalovirus Infected Cells

    DEFF Research Database (Denmark)

    Spiess, Katja; Jeppesen, Mads G.; Malmgaard-Clausen, Mikkel

    2017-01-01

    of human cytomegalovirus (HCMV) infections. US28 is expressed on virus-infected cells and scavenge chemokines by rapid internalization. The chemokine-based fusion-toxin protein (FTP) consisted of a variant (F49A) of CX3CL1 specifically targeting US28 linked to the catalytic domain of Pseudomonas exotoxin...... A (PE). Here, we systematically seek to improve F49A-FTP by modifications in its three structural domains; we generated variants with (1) altered chemokine sequence (K14A, F49L, and F49E), (2) shortened and elongated linker region, and (3) modified toxin domain. Only F49L-FTP displayed higher...... selectivity in its binding to US28 versus CX3CR1, the endogenous receptor for CX3CL1, but this was not matched by a more selective killing of US28-expressing cells. A longer linker and different toxin variants decreased US28 affinity and selective killing. Thereby, F49A-FTP represents the best candidate...

  14. Selectivity on-target of bromodomain chemical probes by structure-guided medicinal chemistry and chemical biology.

    Science.gov (United States)

    Galdeano, Carles; Ciulli, Alessio

    2016-09-01

    Targeting epigenetic proteins is a rapidly growing area for medicinal chemistry and drug discovery. Recent years have seen an explosion of interest in developing small molecules binding to bromodomains, the readers of acetyl-lysine modifications. A plethora of co-crystal structures has motivated focused fragment-based design and optimization programs within both industry and academia. These efforts have yielded several compounds entering the clinic, and many more are increasingly being used as chemical probes to interrogate bromodomain biology. High selectivity of chemical probes is necessary to ensure biological activity is due to an on-target effect. Here, we review the state-of-the-art of bromodomain-targeting compounds, focusing on the structural basis for their on-target selectivity or lack thereof. We also highlight chemical biology approaches to enhance on-target selectivity.

  15. The Gaseous Environments of Quasars: Outflows, Feedback & Cold Mode Accretion

    Science.gov (United States)

    Chen, Chen; Hamann, Fred

    2018-06-01

    The early stages of massive galaxy evolution can involve galaxy-scale outflows driven by a starburst or a central quasar and cold-mode accretion (infall) that adds to the mass buildup in the galaxies. I will describe three related studies that use quasar absorption lines to measure outflows, infall, and the general gaseous environments of quasars across a range of spatial scales. The three studies are: 1) High-resolution spectroscopy with Keck-HIRES and VLT-UVES to study associated absorption lines (AALs) that have redshifts greater than the emission redshifts indicating infall and/or rich multi-component AAL complexes that might be interstellar clouds in the host galaxies that have been shredded and dispersed by a fast unseen quasar-driven wind. The data provide strong constraints on the gas kinematics, spatial structure, column densities, metallicities, and energetics. 2) A complete inventory of high-velocity CIV 1548,1550 mini-BAL outflows in quasars using high-resolution high signal-to-noise spectra in the public VLT-UVES and Keck-HIRES archives. This sensitive mini-BAL survey fills an important niche between previous work on narrow absorption lines (NALs) and the much-studied broad absorption lines (BALs) to build a more complete picture of quasar outflows. I will report of the mini-BAL statistics, the diversity of lines detected, and some tests for correlations with the quasar properties. We find, for example, that mini-BALs at v > 4000 km/s in at least 10% of 511 quasars studied, including 1% at v > 0.1 c. Finally, 3) Use the much larger database of NALs measured in 262,449 BOSS quasars by York et al. (in prep.) to study their potential relationships to the quasars and, specifically, their origins in quasar outflows. This involves primarily comparisons of the incidence and properties of NALs at different velocity shifts to other measured properties of the quasars such as BAL outflows, emission line characteristics, radio-loudness, and red colors. We find

  16. Discovery of a selective catalytic p300/CBP inhibitor that targets lineage-specific tumours

    Energy Technology Data Exchange (ETDEWEB)

    Lasko, Loren M.; Jakob, Clarissa G.; Edalji, Rohinton P.; Qiu, Wei; Montgomery, Debra; Digiammarino, Enrico L.; Hansen, T. Matt; Risi, Roberto M.; Frey, Robin; Manaves, Vlasios; Shaw, Bailin; Algire, Mikkel; Hessler, Paul; Lam, Lloyd T.; Uziel, Tamar; Faivre, Emily; Ferguson, Debra; Buchanan, Fritz G.; Martin, Ruth L.; Torrent, Maricel; Chiang, Gary G.; Karukurichi, Kannan; Langston, J. William; Weinert, Brian T.; Choudhary, Chunaram; de Vries, Peter; Van Drie, John H.; McElligott, David; Kesicki, Ed; Marmorstein, Ronen; Sun, Chaohong; Cole, Philip A.; Rosenberg, Saul H.; Michaelides, Michael R.; Lai, Albert; Bromberg, Kenneth D. (AbbVie); (UCopenhagen); (Petra Pharma); (UPENN); (JHU); (Van Drie); (Faraday)

    2017-09-27

    The dynamic and reversible acetylation of proteins, catalysed by histone acetyltransferases (HATs) and histone deacetylases (HDACs), is a major epigenetic regulatory mechanism of gene transcription1 and is associated with multiple diseases. Histone deacetylase inhibitors are currently approved to treat certain cancers, but progress on the development of drug-like histone actyltransferase inhibitors has lagged behind2. The histone acetyltransferase paralogues p300 and CREB-binding protein (CBP) are key transcriptional co-activators that are essential for a multitude of cellular processes, and have also been implicated in human pathological conditions (including cancer3). Current inhibitors of the p300 and CBP histone acetyltransferase domains, including natural products4, bi-substrate analogues5 and the widely used small molecule C6466,7, lack potency or selectivity. Here, we describe A-485, a potent, selective and drug-like catalytic inhibitor of p300 and CBP. We present a high resolution (1.95 Å) co-crystal structure of a small molecule bound to the catalytic active site of p300 and demonstrate that A-485 competes with acetyl coenzyme A (acetyl-CoA). A-485 selectively inhibited proliferation in lineage-specific tumour types, including several haematological malignancies and androgen receptor-positive prostate cancer. A-485 inhibited the androgen receptor transcriptional program in both androgen-sensitive and castration-resistant prostate cancer and inhibited tumour growth in a castration-resistant xenograft model. These results demonstrate the feasibility of using small molecule inhibitors to selectively target the catalytic activity of histone acetyltransferases, which may provide effective treatments for transcriptional activator-driven malignancies and diseases.

  17. Selective elimination of senescent cells by mitochondrial targeting is regulated by ANT2

    DEFF Research Database (Denmark)

    Hubackova, Sona; Davidova, Eliska; Rohlenova, Katerina

    2018-01-01

    and development of age-related diseases. We found that the anticancer agent mitochondria-targeted tamoxifen (MitoTam), unlike conventional anticancer agents, kills cancer cells without inducing senescence in vitro and in vivo. Surprisingly, it also selectively eliminates both malignant and non-cancerous senescent...... cells. In naturally aged mice treated with MitoTam for 4 weeks, we observed a significant decrease of senescence markers in all tested organs compared to non-treated animals. Mechanistically, we found that the susceptibility of senescent cells to MitoTam is linked to a very low expression level...... of adenine nucleotide translocase-2 (ANT2), inherent to the senescent phenotype. Restoration of ANT2 in senescent cells resulted in resistance to MitoTam, while its downregulation in non-senescent cells promoted their MitoTam-triggered elimination. Our study documents a novel, translationally intriguing role...

  18. Multi-data integration of exploration criteria and selection of prospecting targets

    International Nuclear Information System (INIS)

    Dechang, L.; Jingke, Z.; Maorong, S.; Guojuan, W.

    1991-01-01

    In this paper based on the analysis of the exploration criteria for Shengyuan Basin-a uranium ore field, the multi-data integration and information extraction of exploration criteria are carried out on computer and image processing system so that the areas with best combinations of exploration criteria are directly displayed on the screen. Six prospecting targets are selected through the field examination. Shengyuan basin in Jiangxi province is a uranium-producing, Jurassic Cretaceous volcanic-sedimentary basin with an area of about 400 sq km. Its basement consists of Sinian-Cambrian rocks with Caledonian granites intruded. Several uranium deposits, occurrences and anomalies were discovered over the basin region which, therefore, becomes a very important uranium ore field in China

  19. New Molecules and Old Drugs as Emerging Approaches to Selectively Target Human Glioblastoma Cancer Stem Cells

    Directory of Open Access Journals (Sweden)

    Roberto Würth

    2014-01-01

    Full Text Available Despite relevant progress obtained by multimodal treatment, glioblastoma (GBM, the most aggressive primary brain tumor, is still incurable. The most encouraging advancement of GBM drug research derives from the identification of cancer stem cells (CSCs, since these cells appear to represent the determinants of resistance to current standard therapies. The goal of most ongoing studies is to identify drugs able to affect CSCs biology, either inducing selective toxicity or differentiating this tumor cell population into nontumorigenic cells. Moreover, the therapeutic approach for GBM could be improved interfering with chemo- or radioresistance mechanisms, microenvironment signals, and the neoangiogenic process. During the last years, molecular targeted compounds such as sorafenib and old drugs, like metformin, displayed interesting efficacy in preclinical studies towards several tumors, including GBM, preferentially affecting CSC viability. In this review, the latest experimental results, controversies, and prospective application concerning these promising anticancer drugs will be discussed.

  20. Gene Therapy for Advanced Melanoma: Selective Targeting and Therapeutic Nucleic Acids

    Directory of Open Access Journals (Sweden)

    Joana R. Viola

    2013-01-01

    Full Text Available Despite recent advances, the treatment of malignant melanoma still results in the relapse of the disease, and second line treatment mostly fails due to the occurrence of resistance. A wide range of mutations are known to prevent effective treatment with chemotherapeutic drugs. Hence, approaches with biopharmaceuticals including proteins, like antibodies or cytokines, are applied. As an alternative, regimens with therapeutically active nucleic acids offer the possibility for highly selective cancer treatment whilst avoiding unwanted and toxic side effects. This paper gives a brief introduction into the mechanism of this devastating disease, discusses the shortcoming of current therapy approaches, and pinpoints anchor points which could be harnessed for therapeutic intervention with nucleic acids. We bring the delivery of nucleic acid nanopharmaceutics into perspective as a novel antimelanoma therapeutic approach and discuss the possibilities for melanoma specific targeting. The latest reports on preclinical and already clinical application of nucleic acids in melanoma are discussed.

  1. Deontic reasoning as a target of selection: reply to Astington and Dack.

    Science.gov (United States)

    Cummins, Denise Dellarosa

    2013-12-01

    In their discussion of young children's deontic reasoning performance, Astington and Dack (2013) made the following claims: (1) Children need more cues to elicit cogent social norm reasoning than adults require, namely, explicit reference to authority; (2) Deontic reasoning improves with age, and this is evidence against a nativist view; (3) All evolutionary explanations of deontic reasoning advantages require positing a ''domain-specific deontic reasoning module."; and (4) young children excel at deontic reasoning because it is easier. Here, I refute each claim. Instead, I argue that (1) Social norm reasoning is one type of deontic reasoning that has been the target of selective pressure; (2) Development does not preclude nativism; (3) Epistemic utterances make no greater processing demands than deontic utterances; and (4) both adult and child norm reasoning performance is strongly influenced by reference to or implication of authority. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Construction and applications of exon-trapping gene-targeting vectors with a novel strategy for negative selection.

    Science.gov (United States)

    Saito, Shinta; Ura, Kiyoe; Kodama, Miho; Adachi, Noritaka

    2015-06-30

    Targeted gene modification by homologous recombination provides a powerful tool for studying gene function in cells and animals. In higher eukaryotes, non-homologous integration of targeting vectors occurs several orders of magnitude more frequently than does targeted integration, making the gene-targeting technology highly inefficient. For this reason, negative-selection strategies have been employed to reduce the number of drug-resistant clones associated with non-homologous vector integration, particularly when artificial nucleases to introduce a DNA break at the target site are unavailable or undesirable. As such, an exon-trap strategy using a promoterless drug-resistance marker gene provides an effective way to counterselect non-homologous integrants. However, constructing exon-trapping targeting vectors has been a time-consuming and complicated process. By virtue of highly efficient att-mediated recombination, we successfully developed a simple and rapid method to construct plasmid-based vectors that allow for exon-trapping gene targeting. These exon-trap vectors were useful in obtaining correctly targeted clones in mouse embryonic stem cells and human HT1080 cells. Most importantly, with the use of a conditionally cytotoxic gene, we further developed a novel strategy for negative selection, thereby enhancing the efficiency of counterselection for non-homologous integration of exon-trap vectors. Our methods will greatly facilitate exon-trapping gene-targeting technologies in mammalian cells, particularly when combined with the novel negative selection strategy.

  3. Antibody Selection for Cancer Target Validation of FSH-Receptor in Immunohistochemical Settings

    Directory of Open Access Journals (Sweden)

    Nina Moeker

    2017-10-01

    Full Text Available Background: The follicle-stimulating hormone (FSH-receptor (FSHR has been reported to be an attractive target for antibody therapy in human cancer. However, divergent immunohistochemical (IHC findings have been reported for FSHR expression in tumor tissues, which could be due to the specificity of the antibodies used. Methods: Three frequently used antibodies (sc-7798, sc-13935, and FSHR323 were validated for their suitability in an immunohistochemical study for FSHR expression in different tissues. As quality control, two potential therapeutic anti-hFSHR Ylanthia® antibodies (Y010913, Y010916 were used. The specificity criteria for selection of antibodies were binding to native hFSHR of different sources, and no binding to non-related proteins. The ability of antibodies to stain the paraffin-embedded Flp-In Chinese hamster ovary (CHO/FSHR cells was tested after application of different epitope retrieval methods. Results: From the five tested anti-hFSHR antibodies, only Y010913, Y010916, and FSHR323 showed specific binding to native, cell-presented hFSHR. Since Ylanthia® antibodies were selected to specifically recognize native FSHR, as required for a potential therapeutic antibody candidate, FSHR323 was the only antibody to detect the receptor in IHC/histochemical settings on transfected cells, and at markedly lower, physiological concentrations (ex., in Sertoli cells of human testes. The pattern of FSH323 staining noticed for ovarian, prostatic, and renal adenocarcinomas indicated that FSHR was expressed mainly in the peripheral tumor blood vessels. Conclusion: Of all published IHC antibodies tested, only antibody FSHR323 proved suitable for target validation of hFSHR in an IHC setting for cancer. Our studies could not confirm the previously reported FSHR overexpression in ovarian and prostate cancer cells. Instead, specific overexpression in peripheral tumor blood vessels could be confirmed after thorough validation of the antibodies used.

  4. Visual encoding and fixation target selection in free viewing: presaccadic brain potentials

    Directory of Open Access Journals (Sweden)

    Andrey R Nikolaev

    2013-06-01

    Full Text Available In scrutinizing a scene, the eyes alternate between fixations and saccades. During a fixation, two component processes can be distinguished: visual encoding and selection of the next fixation target. We aimed to distinguish the neural correlates of these processes in the electrical brain activity prior to a saccade onset. Participants viewed color photographs of natural scenes, in preparation for a change detection task. Then, for each participant and each scene we computed an image heat map, with temperature representing the duration and density of fixations. The temperature difference between the start and end points of saccades was taken as a measure of the expected task-relevance of the information concentrated in specific regions of a scene. Visual encoding was evaluated according to whether subsequent change was correctly detected. Saccades with larger temperature difference were more likely to be followed by correct detection than ones with smaller temperature differences. The amplitude of presaccadic activity over anterior brain areas was larger for correct detection than for detection failure. This difference was observed for short scrutinizing but not for long explorative saccades, suggesting that presaccadic activity reflects top-down saccade guidance. Thus, successful encoding requires local scanning of scene regions which are expected to be task-relevant. Next, we evaluated fixation target selection. Saccades moving up in temperature were preceded by presaccadic activity of higher amplitude than those moving down. This finding suggests that presaccadic activity reflects attention deployed to the following fixation location. Our findings illustrate how presaccadic activity can elucidate concurrent brain processes related to the immediate goal of planning the next saccade and the larger-scale goal of constructing a robust representation of the visual scene.

  5. Non-invasive brain stimulation targeting the right fusiform gyrus selectively increases working memory for faces.

    Science.gov (United States)

    Brunyé, Tad T; Moran, Joseph M; Holmes, Amanda; Mahoney, Caroline R; Taylor, Holly A

    2017-04-01

    The human extrastriate cortex contains a region critically involved in face detection and memory, the right fusiform gyrus. The present study evaluated whether transcranial direct current stimulation (tDCS) targeting this anatomical region would selectively influence memory for faces versus non-face objects (houses). Anodal tDCS targeted the right fusiform gyrus (Brodmann's Area 37), with the anode at electrode site PO10, and cathode at FP2. Two stimulation conditions were compared in a repeated-measures design: 0.5mA versus 1.5mA intensity; a separate control group received no stimulation. Participants completed a working memory task for face and house stimuli, varying in memory load from 1 to 4 items. Individual differences measures assessed trait-based differences in facial recognition skills. Results showed 1.5mA intensity stimulation (versus 0.5mA and control) increased performance at high memory loads, but only with faces. Lower overall working memory capacity predicted a positive impact of tDCS. Results provide support for the notion of functional specialization of the right fusiform regions for maintaining face (but not non-face object) stimuli in working memory, and further suggest that low intensity electrical stimulation of this region may enhance demanding face working memory performance particularly in those with relatively poor baseline working memory skills. Published by Elsevier Inc.

  6. Diversity, expression and mRNA targeting abilities of Argonaute-targeting miRNAs among selected vascular plants.

    Science.gov (United States)

    Jagtap, Soham; Shivaprasad, Padubidri V

    2014-12-02

    Micro (mi)RNAs are important regulators of plant development. Across plant lineages, Dicer-like 1 (DCL1) proteins process long ds-like structures to produce micro (mi) RNA duplexes in a stepwise manner. These miRNAs are incorporated into Argonaute (AGO) proteins and influence expression of RNAs that have sequence complementarity with miRNAs. Expression levels of AGOs are greatly regulated by plants in order to minimize unwarranted perturbations using miRNAs to target mRNAs coding for AGOs. AGOs may also have high promoter specificity-sometimes expression of AGO can be limited to just a few cells in a plant. Viral pathogens utilize various means to counter antiviral roles of AGOs including hijacking the host encoded miRNAs to target AGOs. Two host encoded miRNAs namely miR168 and miR403 that target AGOs have been described in the model plant Arabidopsis and such a mechanism is thought to be well conserved across plants because AGO sequences are well conserved. We show that the interaction between AGO mRNAs and miRNAs is species-specific due to the diversity in sequences of two miRNAs that target AGOs, sequence diversity among corresponding target regions in AGO mRNAs and variable expression levels of these miRNAs among vascular plants. We used miRNA sequences from 68 plant species representing 31 plant families for this analysis. Sequences of miR168 and miR403 are not conserved among plant lineages, but surprisingly they differ drastically in their sequence diversity and expression levels even among closely related plants. Variation in miR168 expression among plants correlates well with secondary structures/length of loop sequences of their precursors. Our data indicates a complex AGO targeting interaction among plant lineages due to miRNA sequence diversity and sequences of miRNA targeting regions among AGO mRNAs, thus leading to the assumption that the perturbations by viruses that use host miRNAs to target antiviral AGOs can only be species-specific. We also show

  7. Identification of cytotoxic drugs that selectively target tumor cells with MYC overexpression.

    Directory of Open Access Journals (Sweden)

    Anna Frenzel

    Full Text Available Expression of MYC is deregulated in a wide range of human cancers, and is often associated with aggressive disease and poorly differentiated tumor cells. Identification of compounds with selectivity for cells overexpressing MYC would hence be beneficial for the treatment of these tumors. For this purpose we used cell lines with conditional MYCN or c-MYC expression, to screen a library of 80 conventional cytotoxic compounds for their ability to reduce tumor cell viability and/or growth in a MYC dependent way. We found that 25% of the studied compounds induced apoptosis and/or inhibited proliferation in a MYC-specific manner. The activities of the majority of these were enhanced both by c-MYC or MYCN over-expression. Interestingly, these compounds were acting on distinct cellular targets, including microtubules (paclitaxel, podophyllotoxin, vinblastine and topoisomerases (10-hydroxycamptothecin, camptothecin, daunorubicin, doxorubicin, etoposide as well as DNA, RNA and protein synthesis and turnover (anisomycin, aphidicholin, gliotoxin, MG132, methotrexate, mitomycin C. Our data indicate that MYC overexpression sensitizes cells to disruption of specific pathways and that in most cases c-MYC and MYCN overexpression have similar effects on the responses to cytotoxic compounds. Treatment of the cells with topoisomerase I inhibitors led to down-regulation of MYC protein levels, while doxorubicin and the small molecule MYRA-A was found to disrupt MYC-Max interaction. We conclude that the MYC pathway is only targeted by a subset of conventional cytotoxic drugs currently used in the clinic. Elucidating the mechanisms underlying their specificity towards MYC may be of importance for optimizing treatment of tumors with MYC deregulation. Our data also underscores that MYC is an attractive target for novel therapies and that cellular screenings of chemical libraries can be a powerful tool for identifying compounds with a desired biological activity.

  8. Dipeptidyl peptidase IV as a potential target for selective prodrug activation and chemotherapeutic action in cancers.

    Science.gov (United States)

    Dahan, Arik; Wolk, Omri; Yang, Peihua; Mittal, Sachin; Wu, Zhiqian; Landowski, Christopher P; Amidon, Gordon L

    2014-12-01

    The efficacy of chemotherapeutic drugs is often offset by severe side effects attributable to poor selectivity and toxicity to normal cells. Recently, the enzyme dipeptidyl peptidase IV (DPPIV) was considered as a potential target for the delivery of chemotherapeutic drugs. The purpose of this study was to investigate the feasibility of targeting chemotherapeutic drugs to DPPIV as a strategy to enhance their specificity. The expression profile of DPPIV was obtained for seven cancer cell lines using DNA microarray data from the DTP database, and was validated by RT-PCR. A prodrug was then synthesized by linking the cytotoxic drug melphalan to a proline-glycine dipeptide moiety, followed by hydrolysis studies in the seven cell lines with a standard substrate, as well as the glycyl-prolyl-melphalan (GP-Mel). Lastly, cell proliferation studies were carried out to demonstrate enzyme-dependent activation of the candidate prodrug. The relative RT-PCR expression levels of DPPIV in the cancer cell lines exhibited linear correlation with U95Av2 Affymetrix data (r(2) = 0.94), and with specific activity of a standard substrate, glycine-proline-p-nitroanilide (r(2) = 0.96). The significantly higher antiproliferative activity of GP-Mel in Caco-2 cells (GI₅₀ = 261 μM) compared to that in SK-MEL-5 cells (GI₅₀ = 807 μM) was consistent with the 9-fold higher specific activity of the prodrug in Caco-2 cells (5.14 pmol/min/μg protein) compared to SK-MEL-5 cells (0.68 pmol/min/μg protein) and with DPPIV expression levels in these cells. Our results demonstrate the great potential to exploit DPPIV as a prodrug activating enzyme for efficient chemotherapeutic drug targeting.

  9. THE DEMOGRAPHICS OF BROAD-LINE QUASARS IN THE MASS-LUMINOSITY PLANE. II. BLACK HOLE MASS AND EDDINGTON RATIO FUNCTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Brandon C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93107 (United States); Shen, Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)

    2013-02-10

    We employ a flexible Bayesian technique to estimate the black hole (BH) mass and Eddington ratio functions for Type 1 (i.e., broad line) quasars from a uniformly selected data set of {approx}58, 000 quasars from the Sloan Digital Sky Survey (SDSS) DR7. We find that the SDSS becomes significantly incomplete at M {sub BH} {approx}< 3 Multiplication-Sign 10{sup 8} M {sub Sun} or L/L {sub Edd} {approx}< 0.07, and that the number densities of Type 1 quasars continue to increase down to these limits. Both the mass and Eddington ratio functions show evidence of downsizing, with the most massive and highest Eddington ratio BHs experiencing Type 1 quasar phases first, although the Eddington ratio number densities are flat at z < 2. We estimate the maximum Eddington ratio of Type 1 quasars in the observable universe to be L/L {sub Edd} {approx} 3. Consistent with our results in Shen and Kelly, we do not find statistical evidence for a so-called sub-Eddington boundary in the mass-luminosity plane of broad-line quasars, and demonstrate that such an apparent boundary in the observed distribution can be caused by selection effect and errors in virial BH mass estimates. Based on the typical Eddington ratio in a given mass bin, we estimate growth times for the BHs in Type 1 quasars and find that they are comparable to or longer than the age of the universe, implying an earlier phase of accelerated (i.e., with higher Eddington ratios) and possibly obscured growth. The large masses probed by our sample imply that most of our BHs reside in what are locally early-type galaxies, and we interpret our results within the context of models of self-regulated BH growth.

  10. BCL-2 inhibition targets oxidative phosphorylation and selectively eradicates quiescent human leukemia stem cells

    Science.gov (United States)

    Lagadinou, Eleni D.; Sach, Alexander; Callahan, Kevin; Rossi, Randall M.; Neering, Sarah J.; Minhajuddin, Mohammad; Ashton, John M.; Pei, Shanshan; Grose, Valerie; O’Dwyer, Kristen M.; Liesveld, Jane L.; Brookes, Paul S.; Becker, Michael W.; Jordan, Craig T.

    2013-01-01

    Summary Most forms of chemotherapy employ mechanisms involving induction of oxidative stress, a strategy that can be effective due to the elevated oxidative state commonly observed in cancer cells. However, recent studies have shown that relative redox levels in primary tumors can be heterogeneous, suggesting that regimens dependent on differential oxidative state may not be uniformly effective. To investigate this issue in hematological malignancies, we evaluated mechanisms controlling oxidative state in primary specimens derived from acute myelogenous leukemia (AML) patients. Our studies demonstrate three striking findings. First, the majority of functionally-defined leukemia stem cells (LSCs) are characterized by relatively low levels of reactive oxygen species (termed “ROS-low”). Second, ROS-low LSCs aberrantly over-express BCL-2. Third, BCL-2 inhibition reduced oxidative phosphorylation and selectively eradicated quiescent LSCs. Based on these findings, we propose a model wherein the unique physiology of ROS-low LSCs provides an opportunity for selective targeting via disruption of BCL-2-dependent oxidative phosphorylation. PMID:23333149

  11. THE ULTRAVIOLET-TO-MID-INFRARED SPECTRAL ENERGY DISTRIBUTION OF WEAK EMISSION LINE QUASARS

    International Nuclear Information System (INIS)

    Lane, Ryan A.; Shemmer, Ohad; Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Anderson, Scott F.; Brandt, W. N.; Schneider, Donald P.; Plotkin, Richard M.; Richards, Gordon T.; Strauss, Michael A.

    2011-01-01

    We present Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey (SDSS) quasars at 2.7 ≤ z ≤ 5.9 which have weak or undetectable high-ionization emission lines in their rest-frame ultraviolet (UV) spectra (hereafter weak-lined quasars, or WLQs). The Spitzer data are combined with SDSS spectra and ground-based, near-infrared (IR) photometry of these sources to produce a large inventory of spectral energy distributions (SEDs) of WLQs across the rest-frame ∼0.1-5 μm spectral band. The SEDs of our sources are inconsistent with those of BL Lacertae objects which are dominated by synchrotron emission due to a jet aligned close to our line of sight, but are consistent with the SED of ordinary quasars with similar luminosities and redshifts that exhibit a near-to-mid-IR 'bump', characteristic of hot dust emission. This indicates that broad emission lines in WLQs are intrinsically weak, rather than suffering continuum dilution from a jet, and that such sources cannot be selected efficiently from traditional photometric surveys.

  12. THE ULTRAVIOLET-TO-MID-INFRARED SPECTRAL ENERGY DISTRIBUTION OF WEAK EMISSION LINE QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Ryan A.; Shemmer, Ohad [Department of Physics, University of North Texas, Denton, TX 76203 (United States); Diamond-Stanic, Aleksandar M. [Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093 (United States); Fan Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Anderson, Scott F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Brandt, W. N.; Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Plotkin, Richard M. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam (Netherlands); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Strauss, Michael A., E-mail: RyanLane@my.unt.edu, E-mail: ohad@unt.edu [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States)

    2011-12-20

    We present Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey (SDSS) quasars at 2.7 {<=} z {<=} 5.9 which have weak or undetectable high-ionization emission lines in their rest-frame ultraviolet (UV) spectra (hereafter weak-lined quasars, or WLQs). The Spitzer data are combined with SDSS spectra and ground-based, near-infrared (IR) photometry of these sources to produce a large inventory of spectral energy distributions (SEDs) of WLQs across the rest-frame {approx}0.1-5 {mu}m spectral band. The SEDs of our sources are inconsistent with those of BL Lacertae objects which are dominated by synchrotron emission due to a jet aligned close to our line of sight, but are consistent with the SED of ordinary quasars with similar luminosities and redshifts that exhibit a near-to-mid-IR 'bump', characteristic of hot dust emission. This indicates that broad emission lines in WLQs are intrinsically weak, rather than suffering continuum dilution from a jet, and that such sources cannot be selected efficiently from traditional photometric surveys.

  13. Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yan-Fei [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Green, Paul J.; Pancoast, Anna; MacLeod, Chelsea L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Morganson, Eric; Shen, Yue [Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Brandt, W. N.; Grier, C. J. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Rix, H.-W. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Protopapas, Pavlos [Institute for Applied Computational Science, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States); Scott, Caroline [Astrophysics, Imperial College London, Blackett Laboratory, London SW7 2AZ (United Kingdom); Burgett, W. S.; Hodapp, K. W.; Huber, M. E.; Kaiser, N.; Kudritzki, R. P.; Magnier, E. A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 (United States); and others

    2017-02-20

    We study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band ( g , r , i , z ) light curves in the Pan-STARRS Medium Deep Fields. As photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. We select 240 quasars with redshifts of z ≈ 1 or z ≈ 0.3 that are relatively emission-line free. The light curves are sampled from day to month timescales, which makes it possible to detect lags on the scale of the light crossing time of the accretion disks. With the code JAVELIN , we detect typical lags of several days in the rest frame between the g band and the riz bands. The detected lags are ∼2–3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC 5548 and microlensing measurements of quasars. The lags in our sample are found to increase with increasing luminosity. Furthermore, the increase in lags going from g − r to g − i and then to g − z is slower than predicted in the thin disk model, particularly for high-luminosity quasars. The radial temperature profile in the disk must be different from what is assumed. We also find evidence that the lags decrease with increasing line ratios between ultraviolet Fe ii lines and Mg ii, which may point to changes in the accretion disk structure at higher metallicity.

  14. A search for optical variability of type 2 quasars in SDSS stripe 82

    International Nuclear Information System (INIS)

    Barth, Aaron J.; Carson, Daniel J.; Voevodkin, Alexey; Woźniak, Przemysław

    2014-01-01

    Hundreds of Type 2 quasars have been identified in Sloan Digital Sky Survey (SDSS) data, and there is substantial evidence that they are generally galaxies with highly obscured central engines, in accord with unified models for active galactic nuclei (AGNs). A straightforward expectation of unified models is that highly obscured Type 2 AGNs should show little or no optical variability on timescales of days to years. As a test of this prediction, we have carried out a search for variability in Type 2 quasars in SDSS Stripe 82 using difference-imaging photometry. Starting with the Type 2 AGN catalogs of Zakamska et al. and Reyes et al., we find evidence of significant g-band variability in 17 out of 173 objects for which light curves could be measured from the Stripe 82 data. To determine the nature of this variability, we obtained new Keck spectropolarimetry observations for seven of these variable AGNs. The Keck data show that these objects have low continuum polarizations (p ≲ 1% in most cases) and all seven have broad Hα and/or Mg II emission lines in their total (unpolarized) spectra, indicating that they should actually be classified as Type 1 AGNs. We conclude that the primary reason variability is found in the SDSS-selected Type 2 AGN samples is that these samples contain a small fraction of Type 1 AGNs as contaminants, and it is not necessary to invoke more exotic possible explanations such as a population of 'naked' or unobscured Type 2 quasars. Aside from misclassified Type 1 objects, the Type 2 quasars do not generally show detectable optical variability over the duration of the Stripe 82 survey.

  15. Identification of genomic variants putatively targeted by selection during dog domestication.

    Science.gov (United States)

    Cagan, Alex; Blass, Torsten

    2016-01-12

    Dogs [Canis lupus familiaris] were the first animal species to be domesticated and continue to occupy an important place in human societies. Recent studies have begun to reveal when and where dog domestication occurred. While much progress has been made in identifying the genetic basis of phenotypic differences between dog breeds we still know relatively little about the genetic changes underlying the phenotypes that differentiate all dogs from their wild progenitors, wolves [Canis lupus]. In particular, dogs generally show reduced aggression and fear towards humans compared to wolves. Therefore, selection for tameness was likely a necessary prerequisite for dog domestication. With the increasing availability of whole-genome sequence data it is possible to try and directly identify the genetic variants contributing to the phenotypic differences between dogs and wolves. We analyse the largest available database of genome-wide polymorphism data in a global sample of dogs 69 and wolves 7. We perform a scan to identify regions of the genome that are highly differentiated between dogs and wolves. We identify putatively functional genomic variants that are segregating or at high frequency [> = 0.75 Fst] for alternative alleles between dogs and wolves. A biological pathways analysis of the genes containing these variants suggests that there has been selection on the 'adrenaline and noradrenaline biosynthesis pathway', well known for its involvement in the fight-or-flight response. We identify 11 genes with putatively functional variants fixed for alternative alleles between dogs and wolves. The segregating variants in these genes are strong candidates for having been targets of selection during early dog domestication. We present the first genome-wide analysis of the different categories of putatively functional variants that are fixed or segregating at high frequency between a global sampling of dogs and wolves. We find evidence that selection has been strongest

  16. THE REDSHIFT DISTRIBUTION OF INTERVENING WEAK Mg II QUASAR ABSORBERS AND A CURIOUS DEPENDENCE ON QUASAR LUMINOSITY

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Jessica L.; Churchill, Christopher W.; Nielsen, Nikole M.; Klimek, Elizabeth S. [New Mexico State University, Las Cruces, NM 88003 (United States); Murphy, Michael T. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Melbourne, VIC 3122 (Australia)

    2013-05-01

    We have identified 469 Mg II {lambda}{lambda}2796, 2803 doublet systems having W{sub r} {>=} 0.02 A in 252 Keck/High Resolution Echelle Spectrometer and UVES/Very Large Telescope quasar spectra over the redshift range 0.1 < z < 2.6. Using the largest sample yet of 188 weak Mg II systems (0.02 A {<=}W{sub r} < 0.3 A), we calculate their absorber redshift path density, dN/dz. We find clear evidence of evolution, with dN/dz peaking at z {approx} 1.2, and that the product of the absorber number density and cross section decreases linearly with increasing redshift; weak Mg II absorbers seem to vanish above z {approx_equal} 2.7. If the absorbers are ionized by the UV background, we estimate number densities of 10{sup 6}-10{sup 9} Mpc{sup -3} for spherical geometries and 10{sup 2}-10{sup 5} Mpc{sup -3} for more sheetlike geometries. We also find that dN/dz toward intrinsically faint versus bright quasars differs significantly for weak and strong (W{sub r} {>=} 1.0 A) absorbers. For weak absorption, dN/dz toward bright quasars is {approx}25% higher than toward faint quasars (10{sigma} at low redshift, 0.4 {<=} z {<=} 1.4, and 4{sigma} at high redshift, 1.4 < z {<=} 2.34). For strong absorption the trend reverses, with dN/dz toward faint quasars being {approx}20% higher than toward bright quasars (also 10{sigma} at low redshift and 4{sigma} at high redshift). We explore scenarios in which beam size is proportional to quasar luminosity and varies with absorber and quasar redshifts. These do not explain dN/dz's dependence on quasar luminosity.

  17. ProSelection: A Novel Algorithm to Select Proper Protein Structure Subsets for in Silico Target Identification and Drug Discovery Research.

    Science.gov (United States)

    Wang, Nanyi; Wang, Lirong; Xie, Xiang-Qun

    2017-11-27

    Molecular docking is widely applied to computer-aided drug design and has become relatively mature in the recent decades. Application of docking in modeling varies from single lead compound optimization to large-scale virtual screening. The performance of molecular docking is highly dependent on the protein structures selected. It is especially challenging for large-scale target prediction research when multiple structures are available for a single target. Therefore, we have established ProSelection, a docking preferred-protein selection algorithm, in order to generate the proper structure subset(s). By the ProSelection algorithm, protein structures of "weak selectors" are filtered out whereas structures of "strong selectors" are kept. Specifically, the structure which has a good statistical performance of distinguishing active ligands from inactive ligands is defined as a strong selector. In this study, 249 protein structures of 14 autophagy-related targets are investigated. Surflex-dock was used as the docking engine to distinguish active and inactive compounds against these protein structures. Both t test and Mann-Whitney U test were used to distinguish the strong from the weak selectors based on the normality of the docking score distribution. The suggested docking score threshold for active ligands (SDA) was generated for each strong selector structure according to the receiver operating characteristic (ROC) curve. The performance of ProSelection was further validated by predicting the potential off-targets of 43 U.S. Federal Drug Administration approved small molecule antineoplastic drugs. Overall, ProSelection will accelerate the computational work in protein structure selection and could be a useful tool for molecular docking, target prediction, and protein-chemical database establishment research.

  18. Steep Hard-X-ray Spectra Indicate Extremely High Accretion Rates in Weak Emission-Line Quasars

    Science.gov (United States)

    Marlar, Andrea; Shemmer, Ohad; Anderson, Scott F.; Brandt, W. Niel; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Luo, Bin; Plotkin, Richard; Richards, Gordon T.; Schneider, Donald P.; Wu, Jianfeng

    2018-06-01

    We present XMM-Newton imaging spectroscopy of ten weak emission-line quasars (WLQs) at 0.928 ≤ z ≤ 3.767, six of which are radio quiet and four which are radio intermediate. The new X-ray data enabled us to measure the hard-X-ray power-law photon index (Γ) in each source with relatively high accuracy. These measurements allowed us to confirm previous reports that WLQs have steeper X-ray spectra, therefore indicating higher accretion rates with respect to "typical" quasars. A comparison between the Γ values of our radio-quiet WLQs and those of a carefully-selected, uniform sample of 84 quasars shows that the first are significantly higher, at the ≥ 3σ level. Collectively, the four radio-intermediate WLQs have lower Γ values with respect to the six radio-quiet WLQs, as may be expected if the spectra of the first group are contaminated by X-ray emission from a jet. These results suggest that, in the absence of significant jet emission along our line of sight, WLQs constitute the extreme high end of the accretion rate distribution in quasars. We detect soft excess emission in our lowest-redshift radio-quiet WLQ, in agreement with previous findings suggesting that the prominence of this feature is associated with a high accretion rate. We have not detected signatures of Compton reflection, Fe Kα lines, or strong variability between two X-ray epochs in any of our WLQs.

  19. Cancer cell-selective promoter recognition accompanies antitumor effect by glucocorticoid receptor-targeted gold nanoparticle

    Science.gov (United States)

    Sau, Samaresh; Agarwalla, Pritha; Mukherjee, Sudip; Bag, Indira; Sreedhar, Bojja; Pal-Bhadra, Manika; Patra, Chitta Ranjan; Banerjee, Rajkumar

    2014-05-01

    Nanoparticles, such as gold nanoparticles (GNP), upon convenient modifications perform multi tasks catering to many biomedical applications. However, GNP or any other type of nanoparticles is yet to achieve the feat of intracellular regulation of endogenous genes of choice such as through manipulation of a gene-promoter in a chromosome. As for gene modulation and delivery, GNP (or other nanoparticles) showed only limited gene therapy potential, which relied on the delivery of `exogenous' genes invoking gene knockdown or replacement. Practically, there are no instances for the nanoparticle-mediated promoter regulation of `endogenous' genes, more so, as a cancer selective phenomenon. In this regard, we report the development of a simple, easily modifiable GNP-formulation, which promoted/up-regulated the expression of a specific category of `endogenous' genes, the glucocorticoid responsive genes. This genetic up-regulation was induced in only cancer cells by modified GNP-mediated transcriptional activation of its cytoplasmic receptor, glucocorticoid receptor (GR). Normal cells and their GR remained primarily unperturbed by this GNP-formulation. The most potent gene up-regulating GNP-formulation down-regulated a cancer-specific proliferative signal, phospho-Akt in cancer cells, which accompanied retardation of tumor growth in the murine melanoma model. We show that GR-targeted GNPs may find potential use in the targeting and modulation of genetic information in cancer towards developing novel anticancer therapeutics.Nanoparticles, such as gold nanoparticles (GNP), upon convenient modifications perform multi tasks catering to many biomedical applications. However, GNP or any other type of nanoparticles is yet to achieve the feat of intracellular regulation of endogenous genes of choice such as through manipulation of a gene-promoter in a chromosome. As for gene modulation and delivery, GNP (or other nanoparticles) showed only limited gene therapy potential, which relied

  20. Uranium exploration target selection for proterozoic iron oxide/breccia complex type deposits in India

    International Nuclear Information System (INIS)

    Dwivedy, K.K.; Sinha, K.K.

    1997-01-01

    Multimetal iron oxide/breccia complex (IOBC) type deposits exemplified by Olympic Dam in Australia, fall under low grade, large tonnage deposits. A multidisciplinary integrated exploration programme consisting of airborne surveys, ground geological surveys, geophysical and geochemical investigations and exploratory drilling, supported adequately by the state of the art analytical facilities, data processing using various software and digital image processing has shown moderate success in the identification of target areas for this type of deposits in the Proterozoic terrains of India. Intracratonic, anorogenic, continental rift to continental margin environment have been identified in a very wide spectrum of rock associations. The genesis and evolution of such associations during the Middle Proterozoic period have been reviewed and applied for target selection in the (i) Son-Narmada rift valley zone; (ii) areas covered by Dongargarh Supergroup of rocks in Madhya Pradesh; (iii) areas exposing ferruginous breccia in the western part of the Singhbhum Shear Zone (SSZ) around Lotapahar; (iv) Siang Group of rocks in Arunachal Pradesh; (v) Crystalline rocks of Garo Hills around Anek; and (vi) Chhotanagpur Gneissic complex in the Bahia-Ulatutoli tract of Ranchi Plateau. Of theses six areas, the Son-Narmada rift area appears to be the most promising area for IOBC type deposits. Considering occurrences of the uranium anomalies near Meraraich, Kundabhati, Naktu and Kudar and positive favourability criteria observed in a wide variety of rocks spatially related to the rifts and shears, certain sectors in Son-Narmada rift zone have been identified as promising for intense subsurface exploration. 20 refs, 4 figs, 1 tab

  1. GLUT1-mediated selective tumor targeting with fluorine containing platinum(II) glycoconjugates.

    Science.gov (United States)

    Liu, Ran; Fu, Zheng; Zhao, Meng; Gao, Xiangqian; Li, Hong; Mi, Qian; Liu, Pengxing; Yang, Jinna; Yao, Zhi; Gao, Qingzhi

    2017-06-13

    Increased glycolysis and overexpression of glucose transporters (GLUTs) are physiological characteristics of human malignancies. Based on the so-called Warburg effect, 18flurodeoxyglucose-positron emission tomography (FDG-PET) has successfully developed as clinical modality for the diagnosis and staging of many cancers. To leverage this glucose transporter mediated metabolic disparity between normal and malignant cells, in the current report, we focus on the fluorine substituted series of glucose, mannose and galactose-conjugated (trans-R,R-cyclohexane-1,2-diamine)-2-flouromalonato-platinum(II) complexes for a comprehensive evaluation on their selective tumor targeting. Besides highly improved water solubility, these sugar-conjugates presented improved cytotoxicity than oxaliplatin in glucose tranporters (GLUTs) overexpressing cancer cell lines and exhibited no cross-resistance to cisplatin. For the highly water soluble glucose-conjugated complex (5a), two novel in vivo assessments were conducted and the results revealed that 5a was more efficacious at a lower equitoxic dose (70% MTD) than oxaliplatin (100% MTD) in HT29 xenograft model, and it was significantly more potent than oxaliplatin in leukemia-bearing DBA/2 mice as well even at equimolar dose levels (18% vs 90% MTD). GLUT inhibitor mediated cell viability analysis, GLUT1 knockdown cell line-based cytotoxicity evaluation, and platinum accumulation study demonstrated that the cellular uptake of the sugar-conjugates was regulated by GLUT1. The higher intrinsic DNA reactivity of the sugar-conjugates was confirmed by kinetic study of platinum(II)-guanosine adduct formation. The mechanistic origin of the antitumor effect of the fluorine complexes was found to be forming the bifunctional Pt-guanine-guanine (Pt-GG) intrastrand cross-links with DNA. The results provide a rationale for Warburg effect targeted anticancer drug design.

  2. Automated selected reaction monitoring data analysis workflow for large-scale targeted proteomic studies.

    Science.gov (United States)

    Surinova, Silvia; Hüttenhain, Ruth; Chang, Ching-Yun; Espona, Lucia; Vitek, Olga; Aebersold, Ruedi

    2013-08-01

    Targeted proteomics based on selected reaction monitoring (SRM) mass spectrometry is commonly used for accurate and reproducible quantification of protein analytes in complex biological mixtures. Strictly hypothesis-driven, SRM assays quantify each targeted protein by collecting measurements on its peptide fragment ions, called transitions. To achieve sensitive and accurate quantitative results, experimental design and data analysis must consistently account for the variability of the quantified transitions. This consistency is especially important in large experiments, which increasingly require profiling up to hundreds of proteins over hundreds of samples. Here we describe a robust and automated workflow for the analysis of large quantitative SRM data sets that integrates data processing, statistical protein identification and quantification, and dissemination of the results. The integrated workflow combines three software tools: mProphet for peptide identification via probabilistic scoring; SRMstats for protein significance analysis with linear mixed-effect models; and PASSEL, a public repository for storage, retrieval and query of SRM data. The input requirements for the protocol are files with SRM traces in mzXML format, and a file with a list of transitions in a text tab-separated format. The protocol is especially suited for data with heavy isotope-labeled peptide internal standards. We demonstrate the protocol on a clinical data set in which the abundances of 35 biomarker candidates were profiled in 83 blood plasma samples of subjects with ovarian cancer or benign ovarian tumors. The time frame to realize the protocol is 1-2 weeks, depending on the number of replicates used in the experiment.

  3. X-RAY AND MULTIWAVELENGTH INSIGHTS INTO THE NATURE OF WEAK EMISSION-LINE QUASARS AT LOW REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Wu Jianfeng; Brandt, W. N.; Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Anderson, Scott F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Diamond-Stanic, Aleksandar M. [Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92903 (United States); Hall, Patrick B. [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON M3J 1P3 (Canada); Plotkin, Richard M. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Shemmer, Ohad, E-mail: jfwu@astro.psu.edu [Department of Physics, University of North Texas, Denton, TX 76203 (United States)

    2012-03-01

    We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of {approx}> 5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars. Several other low-redshift WLQ candidates have normal ratios of X-ray-to-optical/UV flux, and their average X-ray spectral properties are also similar to those of typical radio-quiet quasars. The X-ray weak and X-ray normal WLQ candidates may belong to the same subset of quasars having high-ionization 'shielding gas' covering most of the wind-dominated broad emission-line region, but be viewed at different inclinations. The mid-infrared-to-X-ray spectral energy distributions (SEDs) of these sources are generally consistent with those of typical SDSS quasars, showing that they are not likely to be BL Lac objects with relativistically boosted continua and diluted emission lines. The mid-infrared-to-UV SEDs of most radio-quiet weak-featured AGNs without sensitive X-ray coverage (34 objects) are also consistent with those of typical SDSS quasars. However, one source in our

  4. X-RAY AND MULTIWAVELENGTH INSIGHTS INTO THE NATURE OF WEAK EMISSION-LINE QUASARS AT LOW REDSHIFT

    International Nuclear Information System (INIS)

    Wu Jianfeng; Brandt, W. N.; Schneider, Donald P.; Anderson, Scott F.; Diamond-Stanic, Aleksandar M.; Hall, Patrick B.; Plotkin, Richard M.; Shemmer, Ohad

    2012-01-01

    We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of ∼> 5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars. Several other low-redshift WLQ candidates have normal ratios of X-ray-to-optical/UV flux, and their average X-ray spectral properties are also similar to those of typical radio-quiet quasars. The X-ray weak and X-ray normal WLQ candidates may belong to the same subset of quasars having high-ionization 'shielding gas' covering most of the wind-dominated broad emission-line region, but be viewed at different inclinations. The mid-infrared-to-X-ray spectral energy distributions (SEDs) of these sources are generally consistent with those of typical SDSS quasars, showing that they are not likely to be BL Lac objects with relativistically boosted continua and diluted emission lines. The mid-infrared-to-UV SEDs of most radio-quiet weak-featured AGNs without sensitive X-ray coverage (34 objects) are also consistent with those of typical SDSS quasars. However, one source in our X

  5. Weak Hard X-Ray Emission from Two Broad Absorption Line Quasars Observed with NuStar: Compton-Thick Absorption or Intrinsic X-Ray Weakness?

    Science.gov (United States)

    Luo, B.; Brandt, W. N.; Alexander, D. M.; Harrison, F. A.; Stern, D.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W..; hide

    2013-01-01

    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain approx. or equal to 400-600 hard X-ray (is greater than or equal to 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed N(sub H) is less than or equal to 10(exp24) cm(exp-2). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N(sub H) 7 × 10(exp 24) cm(exp-2) if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe Ka line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.

  6. WEAK HARD X-RAY EMISSION FROM TWO BROAD ABSORPTION LINE QUASARS OBSERVED WITH NuSTAR: COMPTON-THICK ABSORPTION OR INTRINSIC X-RAY WEAKNESS?

    Energy Technology Data Exchange (ETDEWEB)

    Luo, B.; Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Alexander, D. M.; Hickox, R. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Harrison, F. A.; Fuerst, F.; Grefenstette, B. W.; Madsen, K. K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Bauer, F. E. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, F. E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Comastri, A. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Farrah, D. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Fiore, F. [Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone (Italy); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Matt, G. [Dipartimento di Matematica e Fisica, Universita degli Studi Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Ogle, P. [IPAC, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States); and others

    2013-08-01

    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain Almost-Equal-To 400-600 hard X-ray ({approx}> 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed (N{sub H} {approx}< 10{sup 24} cm{sup -2}). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N{sub H} Almost-Equal-To 7 Multiplication-Sign 10{sup 24} cm{sup -2} if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe K{alpha} line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.

  7. A Novel Sensor Selection and Power Allocation Algorithm for Multiple-Target Tracking in an LPI Radar Network

    Directory of Open Access Journals (Sweden)

    Ji She

    2016-12-01

    Full Text Available Radar networks are proven to have numerous advantages over traditional monostatic and bistatic radar. With recent developments, radar networks have become an attractive platform due to their low probability of intercept (LPI performance for target tracking. In this paper, a joint sensor selection and power allocation algorithm for multiple-target tracking in a radar network based on LPI is proposed. It is found that this algorithm can minimize the total transmitted power of a radar network on the basis of a predetermined mutual information (MI threshold between the target impulse response and the reflected signal. The MI is required by the radar network system to estimate target parameters, and it can be calculated predictively with the estimation of target state. The optimization problem of sensor selection and power allocation, which contains two variables, is non-convex and it can be solved by separating power allocation problem from sensor selection problem. To be specific, the optimization problem of power allocation can be solved by using the bisection method for each sensor selection scheme. Also, the optimization problem of sensor selection can be solved by a lower complexity algorithm based on the allocated powers. According to the simulation results, it can be found that the proposed algorithm can effectively reduce the total transmitted power of a radar network, which can be conducive to improving LPI performance.

  8. How Quasar Feedback May Shape the Co-evolutionary Paths

    Energy Technology Data Exchange (ETDEWEB)

    Ishibashi, Wako, E-mail: wako.ishibashi@physik.uzh.ch [Physik-Institut, University of Zurich, Zürich (Switzerland)

    2017-10-17

    Observations point toward some form of “co-evolutionary sequence,” from dust-enshrouded starbursts to luminous unobscured quasars. Active galactic nucleus (AGN) feedback is generally invoked to expel the obscuring dusty gas in a blow-out event, eventually revealing the hidden central quasar. However, the physical mechanism driving AGN feedback, either due to winds or radiation, remains uncertain and is still a source of much debate. We consider quasar feedback, based on radiation pressure on dust, which directly acts on the obscuring dusty gas. We show that AGN radiative feedback is capable of efficiently removing the obscuring cocoon, and driving powerful outflows on galactic scales, consistent with recent observations. I will discuss how such quasar feedback may provide a natural physical interpretation of the observed evolutionary path, and the physical implications in the broader context of black hole-host galaxy co-evolution.

  9. Statistics of gravitational lenses. III. Astrophysical consequences of quasar lensing

    International Nuclear Information System (INIS)

    Ostriker, J.P.; Vietri, M.

    1986-01-01

    The method of Schmidt and Green (1983) for calculating the luminosity function of quasars is combined with gravitational-lensing theory to compute expected properties of lensed systems. Multiple quasar images produced by galaxies are of order 0.001 of the observed quasars, with the numbers over the whole sky calculated to be (0.86, 120, 1600) to limiting B magnitudes of (16, 19, 22). The amount of false evolution is small except for an interesting subset of apparently bright, large-redshift objects for which minilensing by starlike objects may be important. Some of the BL Lac objects may be in this category, with the galaxy identified as the parent object really a foreground object within which stars have lensed a background optically violent variable quasar. 24 references

  10. Report on the Dynamical Evolution of an Axially Symmetric Quasar ...

    Indian Academy of Sciences (India)

    retical arguments together with some numerical evidence. The evolution of the orbits is studied, as mass is transported from the disk to the nucleus. ... galaxies and non-axially symmetric quasar models (see Papadopoulos & Caranicolas.

  11. The Doppler Effect: A Consideration of Quasar Redshifts.

    Science.gov (United States)

    Gordon, Kurtiss J.

    1980-01-01

    Provides information on the calculation of the redshift to blueshift ratio introduced by the transverse Doppler effect at relativistic speeds. Indicates that this shift should be mentioned in discussions of whether quasars are "local" rather than "cosmological" objects. (GS)

  12. DES J0454-4448: discovery of the first luminous z ≥ 6 quasar from the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Reed, S. L.; McMahon, R. G.; Banerji, M.; Becker, G. D.; Gonzalez-Solares, E.; Martini, P.; Ostrovski, F.; Rauch, M.; Abbott, T.; Abdalla, F. B.; Allam, S.; Benoit-Levy, A.; Bertin, E.; Buckley-Geer, E.; Burke, D.; Carnero Rosell, A.; da Costa, L. N.; D' Andrea, C.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Cunha, C. E.; Estrada, J.; Evrard, A. E.; Fausti Neto, A.; Finley, D. A.; Fosalba, P.; Frieman, J.; Gruen, D.; Honscheid, K.; James, D.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; Makler, M.; Marshall, J.; Merritt, K.; Miquel, R.; Mohr, J.; Nord, B.; Ogando, R.; Plazas, A.; Romer, K.; Roodman, A.; Rykoff, E.; Sako, M.; Sanchez, E.; Santiago, B.; Schubnell, M.; Sevilla, I.; Smith, C.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D.; Walker, A.; Wechsler, R. H.

    2015-10-28

    We present the first results of a survey for high-redshift, z ≥ 6, quasars using izY multicolour photometric observations from the Dark Energy Survey (DES). Here we report the discovery and spectroscopic confirmation of the zAB, YAB = 20.2, 20.2 (M1450 = -26.5) quasar DES J0454-4448 with a redshift of z = 6.09±0.02 based on the onset of the Ly α forest and an H I near zone size of 4.1+1.1-1.2 proper Mpc. The quasar was selected as an i-band drop out with i-z = 2.46 and zAB < 21.5 from an area of ~300 deg2. It is the brightest of our 43 candidates and was identified for spectroscopic follow-up solely based on the DES i-z and z-Y colours. The quasar is detected by WISE and has W1AB = 19.68. The discovery of one spectroscopically confirmed quasar with 5.7 < z < 6.5 and zAB ≤ 20.2 is consistent with recent determinations of the luminosity function at z ~ 6. DES when completed will have imaged ~5000 deg2 to YAB = 23.0 (5σ point source) and we expect to discover 50–100 new quasars with z > 6 including 3–10 with z > 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies.

  13. Eight new luminous z ≥ 6 quasars discovered via SED model fitting of VISTA, WISE and Dark Energy Survey Year 1 observations

    International Nuclear Information System (INIS)

    Reed, S. L.; McMahon, R. G.; Martini, P.; Banerji, M.; Auger, M.

    2017-01-01

    Here, we present the discovery and spectroscopic confirmation with the European Southern Observatory New Technology Telescope (NTT) and Gemini South telescopes of eight new, and the rediscovery of two previously known, 6.0 < z < 6.5 quasars with zAB < 21.0. These quasars were photometrically selected without any morphological criteria from 1533 deg2 using spectral energy distribution (SED) model fitting to photometric data from Dark Energy Survey (g, r, i, z, Y), VISTA Hemisphere Survey (J, H, K) and Wide-field Infrared Survey Explorer (W1, W2). The photometric data were fitted with a grid of quasar model SEDs with redshift-dependent Ly α forest absorption and a range of intrinsic reddening as well as a series of low-mass cool star models. Candidates were ranked using an SED-model-based χ2-statistic, which is extendable to other future imaging surveys (e.g. LSST and Euclid). Our spectral confirmation success rate is 100 per cent without the need for follow-up photometric observations as used in other studies of this type. Combined with automatic removal of the main types of non-astrophysical contaminants, the method allows large data sets to be processed without human intervention and without being overrun by spurious false candidates. We also present a robust parametric redshift estimator that gives comparable accuracy to Mg ii and CO-based redshift estimators. We find two z ~6.2 quasars with H ii near zone sizes ≤3 proper Mpc that could indicate that these quasars may be young with ages ≲ 10 6 -10 7 years or lie in over dense regions of the IGM. The z = 6.5 quasar VDES J0224–4711 has JAB = 19.75 and is the second most luminous quasar known with z ≥ 6.5.

  14. Pharmacological targeting of valosin containing protein (VCP) induces DNA damage and selectively kills canine lymphoma cells

    International Nuclear Information System (INIS)

    Nadeau, Marie-Ève; Rico, Charlène; Tsoi, Mayra; Vivancos, Mélanie; Filimon, Sabin; Paquet, Marilène; Boerboom, Derek

    2015-01-01

    lymphoma. The selective activity of EER-1 against lymphoma cells suggests that VCP will represent a clinically useful therapeutic target for the treatment of lymphoma. We further suggest a mechanism of EER-1 action centered on the DNA repair response that may be of central importance for the design and characterization of VCP inhibitory compounds for therapeutic use. The online version of this article (doi:10.1186/s12885-015-1489-1) contains supplementary material, which is available to authorized users

  15. Combinatorial support vector machines approach for virtual screening of selective multi-target serotonin reuptake inhibitors from large compound libraries.

    Science.gov (United States)

    Shi, Z; Ma, X H; Qin, C; Jia, J; Jiang, Y Y; Tan, C Y; Chen, Y Z

    2012-02-01

    Selective multi-target serotonin reuptake inhibitors enhance antidepressant efficacy. Their discovery can be facilitated by multiple methods, including in silico ones. In this study, we developed and tested an in silico method, combinatorial support vector machines (COMBI-SVMs), for virtual screening (VS) multi-target serotonin reuptake inhibitors of seven target pairs (serotonin transporter paired with noradrenaline transporter, H(3) receptor, 5-HT(1A) receptor, 5-HT(1B) receptor, 5-HT(2C) receptor, melanocortin 4 receptor and neurokinin 1 receptor respectively) from large compound libraries. COMBI-SVMs trained with 917-1951 individual target inhibitors correctly identified 22-83.3% (majority >31.1%) of the 6-216 dual inhibitors collected from literature as independent testing sets. COMBI-SVMs showed moderate to good target selectivity in misclassifying as dual inhibitors 2.2-29.8% (majority virtual hits correlate with the reported effects of their predicted targets. COMBI-SVM is potentially useful for searching selective multi-target agents without explicit knowledge of these agents. Copyright © 2011 Elsevier Inc. All rights reserved.

  16. Using Deep Learning for Targeted Data Selection, Improving Satellite Observation Utilization for Model Initialization

    Science.gov (United States)

    Lee, Y. J.; Bonfanti, C. E.; Trailovic, L.; Etherton, B.; Govett, M.; Stewart, J.

    2017-12-01

    At present, a fraction of all satellite observations are ultimately used for model assimilation. The satellite data assimilation process is computationally expensive and data are often reduced in resolution to allow timely incorporation into the forecast. This problem is only exacerbated by the recent launch of Geostationary Operational Environmental Satellite (GOES)-16 satellite and future satellites providing several order of magnitude increase in data volume. At the NOAA Earth System Research Laboratory (ESRL) we are researching the use of machine learning the improve the initial selection of satellite data to be used in the model assimilation process. In particular, we are investigating the use of deep learning. Deep learning is being applied to many image processing and computer vision problems with great success. Through our research, we are using convolutional neural network to find and mark regions of interest (ROI) to lead to intelligent extraction of observations from satellite observation systems. These targeted observations will be used to improve the quality of data selected for model assimilation and ultimately improve the impact of satellite data on weather forecasts. Our preliminary efforts to identify the ROI's are focused in two areas: applying and comparing state-of-art convolutional neural network models using the analysis data from the National Center for Environmental Prediction (NCEP) Global Forecast System (GFS) weather model, and using these results as a starting point to optimize convolution neural network model for pattern recognition on the higher resolution water vapor data from GOES-WEST and other satellite. This presentation will provide an introduction to our convolutional neural network model to identify and process these ROI's, along with the challenges of data preparation, training the model, and parameter optimization.

  17. Probing the dark energy with quasar clustering.

    Science.gov (United States)

    Calvão, M O; de Mello Neto, J R T; Waga, I

    2002-03-04

    We show through Monte Carlo simulations that the Alcock-Paczyński test, as applied to quasar clustering, is a powerful tool to probe the cosmological density and equation of state parameters Omega(m0), Omega(x0), and w. By taking into account the effect of peculiar velocities upon the correlation function we obtain for the Two-Degree Field QSO Redshift Survey the predicted confidence contours for the cosmological constant (w = -1) and spatially flat (Omega(m0)+Omega(x0) = 1) cases. For w = -1, the test is especially sensitive to the difference Omega(m0)-Omega(Lambda0), thus being ideal to combine with cosmic microwave background results. For the flat case, it is competitive with future supernova and galaxy number count tests, besides being complementary to them.

  18. Discovery and spectrophotometry of high-redshift quasars

    International Nuclear Information System (INIS)

    MacAlpine, G.M.; Feldman, F.R.

    1982-01-01

    We report on the discovery and spectrophotometry of 30 new high-redshift quasars, which were detected using the Curtis Schmidt technique. We also discuss new follow-up spectrophotometry for 23 quasar candidates from University of Michigan Lists I--IV. Our program sample contains eight quasars with z>3, at least five objects exhibiting broad absorption troughs, and a pair of quasars which are 1' apart on the sky and nearly identical in redshift, at z near 2.13. The redshift distribution for the majority of quasars in UM List IV suggests that most of the single-line quasar candidates in the UM List have low to moderate redshifts, with the reported line often being Mg II lambda2798 or C III] lambda1909. For 17 high-redshift quasars where lambda912 at the emission-line redshift could be examined, we did not find any definite Lyman limit cutoffs. Although three objects show a decline of the continuum within 100 A of lambda912, we do not believe them to be unambiguous examples for emission-line clouds situated in the line of sight. When our O I lambda1304 measurements are combined with the data of others to yield a composite spectrum, we obtain O I lambda1304/lambda8446 = 1.35. This suggests reddening with E/sub B/-Vroughly-equal0.23. Finally, our data exhibit a correlation between Lyα emission line velocity widths and redshift. The higher z quasars in the sample tend to have narrower lines, due, at least in part, to bias in the detection technique

  19. Optical constancy of the quasar 1928+738

    International Nuclear Information System (INIS)

    Corso, G.J.; Harris, R.W.; Fox, R.; Schultz, J.

    1990-01-01

    It has been suggested that the low-red shift quasar 1928 + 738 be utilized in the establishment of an extragalactic reference frame. We have observed the quasar in blue light during an interval of 137 days and found it essentially constant, varying by no more than about I 0.15 magnitude from its average value. Slowly varying long-term changes are not ruled out and others are encouraged to monitor this source in the future. (author)

  20. Effective collision strengths of quasar ultraviolet emission lines

    International Nuclear Information System (INIS)

    Osterbrock, D.E.; Wallace, R.K.

    1977-01-01

    The best available published collision strengths for excitation of permitted and semiforbidden emission lines of abundant ions observed or expected in quasars have been collected and averaged over Maxwellian velocity distributions. For a few ions for which calculations are not available, extrapolation along isoelectronic sequences or in principal quantum number n was used to estimate values. These collision strengths were used to correct differentially published photoionization models of quasars, and the corrected models compared with published observational data

  1. THE FIRST HIGH-REDSHIFT QUASAR FROM Pan-STARRS

    Energy Technology Data Exchange (ETDEWEB)

    Morganson, Eric; De Rosa, Gisella; Decarli, Roberto; Walter, Fabian; Rix, Hans-Walter [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany); Chambers, Ken; Burgett, William; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nick; Magnier, Eugene; Sweeney, Bill; Waters, Christopher [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); McGreer, Ian; Fan, Xiaohui [Steward Observatory, University of Arizona, 933 N Cherry Ave., Tucson, AZ 85721 (United States); Greiner, Jochen [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching (Germany); Price, Paul, E-mail: morganson@mpia.de [Princeton University Observatory, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)

    2012-06-15

    We present the discovery of the first high-redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i{sub P1} dropout in PS1, confirmed photometrically with the SAO Wide-field InfraRed Camera at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph at the Calar Alto 3.5 m telescope. Its near-infrared spectrum was taken at the Large Binocular Telescope Observatory (LBT) with the LBT Near-Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research. It has a redshift of 5.73, an AB z{sub P1} magnitude of 19.4, a luminosity of 3.8 Multiplication-Sign 10{sup 47} erg s{sup -1}, and a black hole mass of 6.9 Multiplication-Sign 10{sup 9} M{sub Sun }. It is a broad absorption line quasar with a prominent Ly{beta} peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high-redshift quasar search that is projected to discover more than 100 i{sub P1} dropout quasars and could potentially find more than 10 z{sub P1} dropout (z > 6.8) quasars.

  2. Quasar Winds as Dust Factories at High Redshift

    OpenAIRE

    Elvis, Martin; Marengo, Massimo; Karovska, Margarita

    2003-01-01

    Winds from AGN and quasars will form large amounts of dust, as the cool gas in these winds passes through the (pressure, temperature) region where dust is formed in AGB stars. Conditions in the gas are benign to dust at these radii. As a result quasar winds may be a major source of dust at high redshifts, obviating a difficulty with current observations, and requiring far less dust to exist at early epochs.

  3. Broad Absorption Line Quasar catalogues with Supervised Neural Networks

    International Nuclear Information System (INIS)

    Scaringi, Simone; Knigge, Christian; Cottis, Christopher E.; Goad, Michael R.

    2008-01-01

    We have applied a Learning Vector Quantization (LVQ) algorithm to SDSS DR5 quasar spectra in order to create a large catalogue of broad absorption line quasars (BALQSOs). We first discuss the problems with BALQSO catalogues constructed using the conventional balnicity and/or absorption indices (BI and AI), and then describe the supervised LVQ network we have trained to recognise BALQSOs. The resulting BALQSO catalogue should be substantially more robust and complete than BI-or AI-based ones.

  4. Star formation quenching in quasar host galaxies

    Science.gov (United States)

    Carniani, Stefano

    2017-10-01

    Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN). In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionised and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ˜2.4 obtained with SINFONI in the H- and K-band. All the quasars show [OIII]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM anti-correlated with star-formation powered emission, i.e. star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50 - 100 M⊙/yr, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2) ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2) transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

  5. Interval MULTIMOORA method with target values of attributes based on interval distance and preference degree: biomaterials selection

    Science.gov (United States)

    Hafezalkotob, Arian; Hafezalkotob, Ashkan

    2017-06-01

    A target-based MADM method covers beneficial and non-beneficial attributes besides target values for some attributes. Such techniques are considered as the comprehensive forms of MADM approaches. Target-based MADM methods can also be used in traditional decision-making problems in which beneficial and non-beneficial attributes only exist. In many practical selection problems, some attributes have given target values. The values of decision matrix and target-based attributes can be provided as intervals in some of such problems. Some target-based decision-making methods have recently been developed; however, a research gap exists in the area of MADM techniques with target-based attributes under uncertainty of information. We extend the MULTIMOORA method for solving practical material selection problems in which material properties and their target values are given as interval numbers. We employ various concepts of interval computations to reduce degeneration of uncertain data. In this regard, we use interval arithmetic and introduce innovative formula for interval distance of interval numbers to create interval target-based normalization technique. Furthermore, we use a pairwise preference matrix based on the concept of degree of preference of interval numbers to calculate the maximum, minimum, and ranking of these numbers. Two decision-making problems regarding biomaterials selection of hip and knee prostheses are discussed. Preference degree-based ranking lists for subordinate parts of the extended MULTIMOORA method are generated by calculating the relative degrees of preference for the arranged assessment values of the biomaterials. The resultant rankings for the problem are compared with the outcomes of other target-based models in the literature.

  6. Vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH.

    Science.gov (United States)

    Yun, Jihye; Mullarky, Edouard; Lu, Changyuan; Bosch, Kaitlyn N; Kavalier, Adam; Rivera, Keith; Roper, Jatin; Chio, Iok In Christine; Giannopoulou, Eugenia G; Rago, Carlo; Muley, Ashlesha; Asara, John M; Paik, Jihye; Elemento, Olivier; Chen, Zhengming; Pappin, Darryl J; Dow, Lukas E; Papadopoulos, Nickolas; Gross, Steven S; Cantley, Lewis C

    2015-12-11

    More than half of human colorectal cancers (CRCs) carry either KRAS or BRAF mutations and are often refractory to approved targeted therapies. We found that cultured human CRC cells harboring KRAS or BRAF mutations are selectively killed when exposed to high levels of vitamin C. This effect is due to increased uptake of the oxidized form of vitamin C, dehydroascorbate (DHA), via the GLUT1 glucose transporter. Increased DHA uptake causes oxidative stress as intracellular DHA is reduced to vitamin C, depleting glutathione. Thus, reactive oxygen species accumulate and inactivate glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Inhibition of GAPDH in highly glycolytic KRAS or BRAF mutant cells leads to an energetic crisis and cell death not seen in KRAS and BRAF wild-type cells. High-dose vitamin C impairs tumor growth in Apc/Kras(G12D) mutant mice. These results provide a mechanistic rationale for exploring the therapeutic use of vitamin C for CRCs with KRAS or BRAF mutations. Copyright © 2015, American Association for the Advancement of Science.

  7. Fluorinated Nucleotide Modifications Modulate Allele Selectivity of SNP-Targeting Antisense Oligonucleotides

    Directory of Open Access Journals (Sweden)

    Michael E. Østergaard

    2017-06-01

    Full Text Available Antisense oligonucleotides (ASOs have the potential to discriminate between subtle RNA mismatches such as SNPs. Certain mismatches, however, allow ASOs to bind at physiological conditions and result in RNA cleavage mediated by RNase H. We showed that replacing DNA nucleotides in the gap region of an ASO with other chemical modification can improve allele selectivity. Herein, we systematically substitute every position in the gap region of an ASO targeting huntingtin gene (HTT with fluorinated nucleotides. Potency is determined in cell culture against mutant HTT (mtHTT and wild-type HTT (wtHTT mRNA and RNase H cleavage intensities, and patterns are investigated. This study profiled five different fluorinated nucleotides and showed them to have predictable, site-specific effects on RNase H cleavage, and the cleavage patterns were rationalized from a published X-ray structure of human RNase H1. The results herein can be used as a guide for future projects where ASO discrimination of SNPs is important.

  8. Green tea extract selectively targets nanomechanics of live metastatic cancer cells

    International Nuclear Information System (INIS)

    Cross, Sarah E; Gimzewski, James K; Jin Yusheng; Lu Qingyi; Rao Jianyu

    2011-01-01

    Green tea extract (GTE) is known to be a potential anticancer agent (Yang et al 2009 Nat. Rev. Cancer 9 429-39) with various biological activities (Lu et al 2005 Clin. Cancer Res. 11 1675-83; Yang et al 1998 Carcinogenesis 19 611-6) yet the precise mechanism of action is still unclear. The biomechanical response of GTE treated cells taken directly from patient's body samples was measured using atomic force microscopy (AFM) (Binnig et al 1986 Phys. Rev. Lett. 56 930). We found significant increase in stiffness of GTE treated metastatic tumor cells, with a resulting value similar to untreated normal mesothelial cells, whereas mesothelial cell stiffness after GTE treatment is unchanged. Immunofluorescence analysis showed an increase in cytoskeletal-F-actin in GTE treated tumor cells, suggesting GTE treated tumor cells display mechanical, structural and morphological features similar to normal cells, which appears to be mediated by annexin-I expression, as determined by siRNA analysis of an in vitro cell line model. Our data indicates that GTE selectively targets human metastatic cancer cells but not normal mesothelial cells, a finding that is significantly advantageous compared to conventional chemotherapy agents.

  9. One millimeter continuum observations of high redshift quasars

    International Nuclear Information System (INIS)

    Ennis, D.J.; Soifer, B.T.

    1981-01-01

    Upper limits to the one-millimeter continuum flux densities of the high redshift quasars B2 1225 + 31, Ton 490, and PHL 957 are presented. The upper limit to the power observed from these quasars at 1 mm is, on the average, one half of the observed power in the continuum at L-alpha. These observations are used to constrain the temperature of a hypothetical dust shell which reddens the quasar line and continuum emission by an extinction optical depth sufficient to account for the anomalously low L-alpha/H-alpha emission line ratio observed in each of these quasars. For the quasars studied, dust shell temperatures between 25 K and 50 to 95 K are prohibited by the present data. A dust shell at a temperature within this span reradiating all the power absorbed from the quasar ultraviolet continuum would produce a one-millimeter flux density greater than the measured upper limit. The average radius of the model dust shell cannot be between 70 kpc and 1 Mpc

  10. DISSECTING THE QUASAR MAIN SEQUENCE: INSIGHT FROM HOST GALAXY PROPERTIES

    International Nuclear Information System (INIS)

    Sun, Jiayi; Shen, Yue

    2015-01-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical Fe ii strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L Edd ) of the black hole (BH) accretion. Shen and Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing Fe ii strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion σ * (hence, the BH mass via the M–σ * relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ * systematically decreases with increasing Fe ii strength, confirming that the Eddington ratio increases with Fe ii strength. We also found that at fixed luminosity and Fe ii strength, there is little dependence of σ * on the broad Hβ FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties

  11. Circum-Galactic Medium in the Halo of Quasars

    Directory of Open Access Journals (Sweden)

    Riccardo Ottolina

    2017-12-01

    Full Text Available The properties of circum-galactic gas in the halo of quasar host galaxies are investigated analyzing Mg II 2800 and C IV 1540 absorption-line systems along the line of sight close to quasars. We used optical spectroscopy of closely aligned pairs of quasars (projected distance ≤ 200 kpc, but at very different redshift obtained at the VLT and Gran Telescopio Canarias to investigate the distribution of the absorbing gas for a sample of quasars at z ~1. Absorption systems of EW ≥0.3 associated with the foreground quasars are revealed up to 200 kpc from the centre of the host galaxy, showing that the structure of the absorbing gas is patchy with a covering fraction quickly decreasing beyond 100 kpc. In this contribution we use optical and near-IR images obtained at VLT to investigate the relations between the properties of the circum-galactic medium of the host galaxies and of the large scale galaxy environments of the foreground quasars.

  12. The Identification of Z-dropouts in Pan-STARRS1: Three Quasars at 6.5< z< 6.7

    Science.gov (United States)

    Venemans, B. P.; Bañados, E.; Decarli, R.; Farina, E. P.; Walter, F.; Chambers, K. C.; Fan, X.; Rix, H.-W.; Schlafly, E.; McMahon, R. G.; Simcoe, R.; Stern, D.; Burgett, W. S.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Metcalfe, N.; Morgan, J. S.; Price, P. A.; Tonry, J. L.; Waters, C.; AlSayyad, Y.; Banerji, M.; Chen, S. S.; González-Solares, E. A.; Greiner, J.; Mazzucchelli, C.; McGreer, I.; Miller, D. R.; Reed, S.; Sullivan, P. W.

    2015-03-01

    Luminous distant quasars are unique probes of the high-redshift intergalactic medium (IGM) and of the growth of massive galaxies and black holes in the early universe. Absorption due to neutral hydrogen in the IGM makes quasars beyond a redshift of z≃ 6.5 very faint in the optical z band, thus locating quasars at higher redshifts requires large surveys that are sensitive above 1 micron. We report the discovery of three new z\\gt 6.5 quasars, corresponding to an age of the universe of \\lt 850 Myr, selected as z-band dropouts in the Pan-STARRS1 survey. This increases the number of known z\\gt 6.5 quasars from four to seven. The quasars have redshifts of z = 6.50, 6.52, and 6.66, and include the brightest z-dropout quasar reported to date, PSO J036.5078 + 03.0498 with {{M}1450}=-27.4. We obtained near-infrared spectroscopy for the quasars, and from the Mg ii line, we estimate that the central black holes have masses between 5 × 108 and 4 × 109 {{M}⊙ } and are accreting close to the Eddington limit ({{L}Bol}/{{L}Edd}=0.13-1.2). We investigate the ionized regions around the quasars and find near-zone radii of {{R}NZ}=1.5-5.2 proper Mpc, confirming the trend of decreasing near-zone sizes with increasing redshift found for quasars at 5.7\\lt z\\lt 6.4. By combining RNZ of the PS1 quasars with those of 5.7\\lt z\\lt 7.1 quasars in the literature, we derive a luminosity-corrected redshift evolution of {{R}NZ,corrected}=(7.2+/- 0.2)-(6.1+/- 0.7)× (z-6) Mpc. However, the large spread in RNZ in the new quasars implies a wide range in quasar ages and/or a large variation in the neutral hydrogen fraction along different lines of sight. Based in part on observations collected at the European Southern Observatory, Chile, programs 179.A-2010, 092.A-0150, 093.A-0863, and 093.A-0574, and at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC). This paper

  13. A large area search for radio-loud quasars within the epoch of reionization

    OpenAIRE

    Jarvis, Matt J.; Rawlings, Steve; Barrio, F. Eugenio; Hill, Gary J.; Bauer, Amanda; Croft, Steve

    2004-01-01

    The Universe became fully reionized, and observable optically, at a time corresponding to redshift z ~ 6.5, so it is only by studying the HI and molecular absorption lines against higher-redshift, radio-loud sources that one can hope to make detailed studies of the earliest stages of galaxy formation. At present no targets for such studies are known. In these proceedings we describe a survey which is underway to find radio-loud quasars at z > 6.5, and present broad-band SEDs of our most promi...

  14. [Targeted pharmacist-led medication order review in hospital: Assessment of a selection method for drug prescriptions].

    Science.gov (United States)

    Jarre, C; Bouchet, J; Hellot-Guersing, M; Leromain, A-S; Derharoutunian, C; Gadot, A; Roubille, R

    2017-11-01

    The aim of this study was to assess a selection method for drug prescriptions developed at the hospital level that allows to target pharmacist-led medication order review for at-risk patients and drugs. A one-month study has been conducted on all targeted medication orders in 19 care units. Selection criteria have been identified: biological criteria, alert medications and drug interactions. Pharmacists' interventions proposed during medication order review were listed and the possible links to the selection criteria were determined. A total of 1612 prescriptions were analysed and 236 pharmacists' interventions were performed (14.6 interventions per 100 prescriptions). Physicians' acceptance rate was 60.6%. The percentage of pharmacists' interventions linked to the selection criteria was 35.6%. The relevance of the biological criteria was identified, particularly the one identifying patients with creatinine clearance below 30ml/min. Six alert medications were also relevant selection criteria: dabigatran, morphine, gentamicin, methotrexate, potassium chloride and trimethoprim sulfamethoxazole. Drug interactions criteria was irrelevant. This study allowed a first assessment of the selection criteria used. A largest study seems necessary to continue the analysis of this selection method for prescriptions, especially the assessment of the alert medications list, in order to refine the prescriptions targeting. Copyright © 2017 Académie Nationale de Pharmacie. Published by Elsevier Masson SAS. All rights reserved.

  15. Attention Blinks for Selection, Not Perception or Memory: Reading Sentences and Reporting Targets

    Science.gov (United States)

    Potter, Mary C.; Wyble, Brad; Olejarczyk, Jennifer

    2011-01-01

    In whole report, a sentence presented sequentially at the rate of about 10 words/s can be recalled accurately, whereas if the task is to report only two target words (e.g., red words), the second target suffers an attentional blink if it appears shortly after the first target. If these two tasks are carried out simultaneously, is there an…

  16. Deciding Where to Attend: Priming of Pop-Out Drives Target Selection

    Science.gov (United States)

    Brascamp, Jan W.; Blake, Randolph; Kristjansson, Arni

    2011-01-01

    With attention and eye-movements humans orient to targets of interest. This orienting occurs faster when the same target repeats: priming of pop-out (PoP). While reaction times (RTs) can be important, PoP's real function could be to steer "where" to orient, a possibility underexposed in many current paradigms, as these predesignate a target to…

  17. Microbial metabolomics: Replacing trial-and-error by the unbiased selection and ranking of targets

    NARCIS (Netherlands)

    Werf, M.J. van der; Jellema, R.H.; Hankemeier, T.

    2005-01-01

    Microbial production strains are currently improved using a combination of random and targeted approaches. In the case of a targeted approach, potential bottlenecks, feed-back inhibition, and side-routes are removed, and other processes of interest are targeted by overexpressing or knocking-out the

  18. Peering Through the Dust: NuSTAR Observations of Two First-2Mass Red Quasars

    Science.gov (United States)

    Lamassa, Stephanie M.; Ricarte, Angelo; Glikman, Eilat; Urry, C. Megan; Stern, Daniel; Yaqoob, Tahir; Lansbury, George B.; Civano, Francesca; Boggs, Steve E.; Zhang, Will

    2016-01-01

    Some reddened quasars appear to be transitional objects in the paradigm of merger-induced black hole growth/ galaxy evolution, where a heavily obscured nucleus starts to be unveiled by powerful quasar winds evacuating the surrounding cocoon NuSTAR and XMM-Newton/Chandra observations of FIRST-2MASS-selected red quasars F2M 0830+3759 and F2M 1227+3214. We find that though F2M 0830 +3759 is moderately obscured N(sub H) = (2.1 +/- 0.2) x 10 (exp 22) per square centimeter) and F2M 1227+3214 is mildly absorbed (N(sub H),Z =3.4(+0.8/-0.7) X 10(exp -2) along the line of sight, heavier global obscuration may be present in both sources, with N(sub H) = 3.7 (+4.1/-2.6) X 10 (exp 23) per square centimeter) and less than 5.5 X 10(exp 23) per square centimeter) for F2M 0830+3759 and F2M 1227+ 3214, respectively. F2M 0830+3759 also has an excess of soft X-ray emission below 1 of dust and gas. Hard X-ray observations are able to peer through this gas and dust, revealing the properties of circumnuclear obscuration. Here, we present keV, which is well accommodated by a model where 7% of the intrinsic X-ray emission from the active galactic nucleus (AGN) is scattered into the line of sight. While F2M 1227+3214 has a dust-to-gas ratio (E(B - V)/NH) consistent with the Galactic value, the value of E(B - V)/NH for F2M 0830+3759 is lower than the Galactic standard, consistent with the paradigm that the dust resides on galactic scales while the X-ray reprocessing gas originates within the dust sublimation zone of the broad-line region. The X-ray and 6.1 µm luminosities of these red quasars are consistent with the empirical relations derived for high-luminosity, unobscured quasars, extending the parameter space of obscured AGNs previously observed by NuSTAR to higher luminosities.

  19. Quality of diabetes care predicts the development of cardiovascular events: results of the AMD-QUASAR study.

    Science.gov (United States)

    Rossi, Maria C E; Lucisano, Giuseppe; Comaschi, Marco; Coscelli, Carlo; Cucinotta, Domenico; Di Blasi, Patrizia; Bader, Giovanni; Pellegrini, Fabio; Valentini, Umberto; Vespasiani, Giacomo; Nicolucci, Antonio

    2011-02-01

    The QUASAR (Quality Assessment Score and Cardiovascular Outcomes in Italian Diabetes Patients) study aimed to assess whether a quality-of-care summary score predicted the development of cardiovascular (CV) events in patients with type 2 diabetes. In 67 diabetes clinics, data on randomly selected patients were extracted from electronic medical records. The score was calculated using process and outcome indicators based on monitoring, targets, and treatment of A1C, blood pressure, LDL cholesterol, and microalbuminuria. The score ranged from 0 to 40. Overall, 5,181 patients were analyzed; 477 (9.2%) patients developed a CV event after a median follow-up of 28 months. The incidence rate (per 1,000 person-years) of CV events was 62.4 in patients with a score of 25. Multilevel analysis, adjusted for clustering and case-mix, showed that the risk to develop a new CV event was 84% higher in patients with a score of 25. Mean quality score varied across centers from 16.5 ± 7.5 to 29.1 ± 6.3. When the score was tested as the dependent variable, it emerged that 18% of the variance in the score could be attributed to setting characteristics. Our study documented a close relationship between quality of diabetes care and long-term outcomes. A simple score can be used to monitor quality of care and compare the performance of different centers/physicians.

  20. Chemical biology based on target-selective degradation of proteins and carbohydrates using light-activatable organic molecules.

    Science.gov (United States)

    Toshima, Kazunobu

    2013-05-01

    Proteins and carbohydrates play crucial roles in a wide range of biological processes, including serious diseases. The development of novel and innovative methods for selective control of specific proteins and carbohydrates functions has attracted much attention in the field of chemical biology. In this account article, the development of novel chemical tools, which can degrade target proteins and carbohydrates by irradiation with a specific wavelength of light under mild conditions without any additives, is introduced. This novel class of photochemical agents promise bright prospects for finding not only molecular-targeted bioprobes for understanding of the structure-activity relationships of proteins and carbohydrates but also novel therapeutic drugs targeting proteins and carbohydrates.

  1. The Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Quasar Survey: Quasar Properties from Data Release Two and Three

    Science.gov (United States)

    Dong, X. Y.; Wu, Xue-Bing; Ai, Y. L.; Yang, J. Y.; Yang, Q.; Wang, F.; Zhang, Y. X.; Luo, A. L.; Xu, H.; Yuan, H. L.; Zhang, J. N.; Wang, M. X.; Wang, L. L.; Li, Y. B.; Zuo, F.; Hou, W.; Guo, Y. X.; Kong, X.; Chen, X. Y.; Wu, Y.; Yang, H. F.; Yang, M.

    2018-05-01

    This is the second installment for the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Quasar Survey, which includes quasars observed from 2013 September to 2015 June. There are 9024 confirmed quasars in DR2 and 10911 in DR3. After cross-match with the Sloan Digital Sky Survey (SDSS) quasar catalogs and NED, 12126 quasars are discovered independently. Among them, 2225 quasars were released by SDSS DR12 QSO catalog in 2014 after we finalized the survey candidates. 1801 sources were identified by SDSS DR14 as QSOs. The remaining 8100 quasars are considered as newly founded, and among them, 6887 quasars can be given reliable emission line measurements and the estimated black hole masses. Quasars found in LAMOST are mostly located at low-to-moderate redshifts, with a mean value of 1.5. The highest redshift observed in DR2 and DR3 is 5. We applied emission line measurements to Hα, Hβ, Mg II, and C IV. We deduced the monochromatic continuum luminosities using photometry data, and estimated the virial black hole masses for the newly discovered quasars. Results are compiled into a quasar catalog, which will be available online.

  2. Effectiveness of a selective alcohol prevention program targeting personality risk factors: Results of interaction analyses.

    Science.gov (United States)

    Lammers, Jeroen; Goossens, Ferry; Conrod, Patricia; Engels, Rutger; Wiers, Reinout W; Kleinjan, Marloes

    2017-08-01

    To explore whether specific groups of adolescents (i.e., scoring high on personality risk traits, having a lower education level, or being male) benefit more from the Preventure intervention with regard to curbing their drinking behaviour. A clustered randomized controlled trial, with participants randomly assigned to a 2-session coping skills intervention or a control no-intervention condition. Fifteen secondary schools throughout The Netherlands; 7 schools in the intervention and 8 schools in the control condition. 699 adolescents aged 13-15; 343 allocated to the intervention and 356 to the control condition; with drinking experience and elevated scores in either negative thinking, anxiety sensitivity, impulsivity or sensation seeking. Differential effectiveness of the Preventure program was examined for the personality traits group, education level and gender on past-month binge drinking (main outcome), binge frequency, alcohol use, alcohol frequency and problem drinking, at 12months post-intervention. Preventure is a selective school-based alcohol prevention programme targeting personality risk factors. The comparator was a no-intervention control. Intervention effects were moderated by the personality traits group and by education level. More specifically, significant intervention effects were found on reducing alcohol use within the anxiety sensitivity group (OR=2.14, CI=1.40, 3.29) and reducing binge drinking (OR=1.76, CI=1.38, 2.24) and binge drinking frequency (β=0.24, p=0.04) within the sensation seeking group at 12months post-intervention. Also, lower educated young adolescents reduced binge drinking (OR=1.47, CI=1.14, 1.88), binge drinking frequency (β=0.25, p=0.04), alcohol use (OR=1.32, CI=1.06, 1.65) and alcohol use frequency (β=0.47, p=0.01), but not those in the higher education group. Post hoc latent-growth analyses revealed significant effects on the development of binge drinking (β=-0.19, p=0.02) and binge drinking frequency (β=-0.10, p=0

  3. From Target Selection to Post-Stimulation Analysis: Example of an Unconventional Faulted Reservoir

    Science.gov (United States)

    LeCalvez, J. H.; Williams, M.; Xu, W.; Stokes, J.; Moros, H.; Maxwell, S. C.; Conners, S.

    2011-12-01

    As the global balance of supply and demand forces the hydrocarbon industry toward unconventional resources, technology- and economics-driven shale oil and gas production is gaining momentum throughout many basins worldwide. Production from such unconventional plays is facilitated by massive hydraulic fracturing treatments aimed at increasing permeability and reactivating natural fractures. Large-scale faulting and fracturing partly control stress distribution, hence stimulation-derived hydraulically-induced fracture systems development. Therefore, careful integrated approaches to target selection, treatment staging, and stimulation methods need to be used to economically maximize ultimate hydrocarbon recovery. We present a case study of a multistage, multilateral stimulation project in the Fort Worth Basin, Texas. Wells had to be drilled within city limits in a commercially developing building area. Well locations and trajectories were determined in and around large-scale faults using 3D surface seismic with throws varying from seven to thirty meters. As a result, three horizontal wells were drilled in the Lower Barnett Shale section, 150 m apart with the central well landed about 25 m shallower than the outside laterals. Surface seismic indicates that the surface locations are on top of a major fault complex with the lateral sections drilling away from the major fault system and through a smaller fault. Modeling of the borehole-based microseismic monitoring options led to the selection of an optimum set of configurations given the operational restrictions faced: monitoring would mainly take place using a horizontal array to be tractored downhole and moved according to the well and stage to be monitored. Wells were completed using a perf-and-plug approach allowing for each stimulation stage to obtain a precise orientation of the various three-component accelerometers of the monitoring array as well as the calibration of the velocity model used to process the

  4. Selecting aesthetic gynecologic procedures for plastic surgeons: a review of target methodology.

    Science.gov (United States)

    Ostrzenski, Adam

    2013-04-01

    The objective of this article was to assist cosmetic-plastic surgeons in selecting aesthetic cosmetic gynecologic-plastic surgical interventions. Target methodological analyses of pertinent evidence-based scientific papers and anecdotal information linked to surgical techniques for cosmetic-plastic female external genitalia were examined. A search of the existing literature from 1900 through June 2011 was performed by utilizing electronic and manual databases. A total of 87 articles related to cosmetic-plastic gynecologic surgeries were identified in peer-review journals. Anecdotal information was identified in three sources (Barwijuk, Obstet Gynecol J 9(3):2178-2179, 2011; Benson, 5th annual congress on aesthetic vaginal surgery, Tucson, AZ, USA, November 14-15, 2010; Scheinberg, Obstet Gynecol J 9(3):2191, 2011). Among those articles on cosmetic-plastic gynecologic surgical technique that were reviewed, three articles met the criteria for evidence-based medicine level II, one article was level II-1 and two papers were level II-2. The remaining papers were classified as level III. The pertinent 25 papers met the inclusion criteria and were analyzed. There was no documentation on the safety and effectiveness of cosmetic-plastic gynecologic procedures in the scientific literature. All published surgical interventions are not suitable for a cosmetic-plastic practice. The absence of documentation on safety and effectiveness related to cosmetic-plastic gynecologic procedures prevents the establishment of a standard of practice. Traditional gynecologic surgical procedures cannot be labeled and used as cosmetic-plastic procedures, it is a deceptive practice. Obtaining legal trademarks on traditional gynecologic procedures and creating a business model that tries to control clinical-scientific knowledge dissemination is unethical. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings

  5. Nicotine facilitates nicotinic acetylcholine receptor targeting to mitochondria but makes them less susceptible to selective ligands.

    Science.gov (United States)

    Uspenska, Kateryna; Lykhmus, Olena; Gergalova, Galyna; Chernyshov, Volodymyr; Arias, Hugo R; Komisarenko, Sergiy; Skok, Maryna

    2017-08-24

    Several nicotinic acetylcholine receptor (nAChR) subtypes are expressed in mitochondria to regulate the internal pathway of apoptosis in ion channel-independent manner. However, the mechanisms of nAChR activation in mitochondria and targeting to mitochondria are still unknown. Nicotine has been shown to favor nAChR pentamer assembly, folding, and maturation on the way of biosynthesis. The idea of the present work was to determine whether nicotine affects the content, glycosylation, and function of mitochondrial nAChRs. Experiments were performed in isolated liver mitochondria from mice, that either consumed or not nicotine with the drinking water (200μL/L) for 7days. Mitochondria detergent lysates were studied by sandwich or lectin ELISA for the presence and carbohydrate composition of different nAChR subunits. Intact mitochondria were examined by flow cytometry for the binding of fluorescently labeled α-cobratoxin and were tested in functional assay of cytochrome c release under the effect of either Ca 2+ or wortmannin in the presence or absence of nAChR-selective ligands, including PNU-282987 (1nM), dihydro-β-erythroidine (DhβE, 1μM), PNU-120596 (0.3, 3, or 10μM) and desformylflustrabromine hydrochloride (dFBr, 0.001, 0.3, or 1μM). It was found that nicotine consumption increased the ratio of mitochondrial vs non-mitochondrial nAChRs in the liver, enhanced fucosylation of mitochondrial nAChRs, but prevented the binding of α-cobratoxin and the cytochrome c release-attenuating effects of nAChR-specific agonists, antagonists, or positive allosteric modulators. It is concluded that nicotine consumption in vivo favors nAChR glycosylation and trafficking to mitochondria but makes them less susceptible to the effects of specific ligands. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Thioredoxin Selectivity for Thiol-based Redox Regulation of Target Proteins in Chloroplasts*

    Science.gov (United States)

    Yoshida, Keisuke; Hara, Satoshi; Hisabori, Toru

    2015-01-01

    Redox regulation based on the thioredoxin (Trx) system is believed to ensure light-responsive control of various functions in chloroplasts. Five Trx subtypes have been reported to reside in chloroplasts, but their functional diversity in the redox regulation of Trx target proteins remains poorly clarified. To directly address this issue, we studied the Trx-dependent redox shifts of several chloroplast thiol-modulated enzymes in vitro and in vivo. In vitro assays using a series of Arabidopsis recombinant proteins provided new insights into Trx selectivity for the redox regulation as well as the underpinning for previous suggestions. Most notably, by combining the discrimination of thiol status with mass spectrometry and activity measurement, we identified an uncharacterized aspect of the reductive activation of NADP-malate dehydrogenase; two redox-active Cys pairs harbored in this enzyme were reduced via distinct utilization of Trxs even within a single polypeptide. In our in vitro assays, Trx-f was effective in reducing all thiol-modulated enzymes analyzed here. We then investigated the in vivo physiological relevance of these in vitro findings, using Arabidopsis wild-type and Trx-f-deficient plants. Photoreduction of fructose-1,6-bisphosphatase was partially impaired in Trx-f-deficient plants, but the global impact of Trx-f deficiency on the redox behaviors of thiol-modulated enzymes was not as striking as expected from the in vitro data. Our results provide support for the in vivo functionality of the Trx system and also highlight the complexity and plasticity of the chloroplast redox network. PMID:25878252

  7. Cell Density Affects the Detection of Chk1 Target Engagement by the Selective Inhibitor V158411.

    Science.gov (United States)

    Geneste, Clara C; Massey, Andrew J

    2018-02-01

    Understanding drug target engagement and the relationship to downstream pharmacology is critical for drug discovery. Here we have evaluated target engagement of Chk1 by the small-molecule inhibitor V158411 using two different target engagement methods (autophosphorylation and cellular thermal shift assay [CETSA]). Target engagement measured by these methods was subsequently related to Chk1 inhibitor-dependent pharmacology. Inhibition of autophosphorylation was a robust method for measuring V158411 Chk1 target engagement. In comparison, while target engagement determined using CETSA appeared robust, the V158411 CETSA target engagement EC 50 values were 43- and 19-fold greater than the autophosphorylation IC 50 values. This difference was attributed to the higher cell density in the CETSA assay configuration. pChk1 (S296) IC 50 values determined using the CETSA assay conditions were 54- and 33-fold greater than those determined under standard conditions and were equivalent to the CETSA EC 50 values. Cellular conditions, especially cell density, influenced the target engagement of V158411 for Chk1. The effects of high cell density on apparent compound target engagement potency should be evaluated when using target engagement assays that necessitate high cell densities (such as the CETSA conditions used in this study). In such cases, the subsequent relation of these data to downstream pharmacological changes should therefore be interpreted with care.

  8. CORRELATIONS OF QUASAR OPTICAL SPECTRA WITH RADIO MORPHOLOGY

    International Nuclear Information System (INIS)

    Kimball, Amy E.; Ivezic, Zeljko; Wiita, Paul J.; Schneider, Donald P.

    2011-01-01

    Using the largest homogeneous quasar sample with high-quality optical spectra and robust radio morphology classifications assembled to date, we investigate relationships between radio and optical properties with unprecedented statistical power. The sample consists of 4714 radio quasars from FIRST with S 20 ≥ 2 mJy and with spectra from the Sloan Digital Sky Survey (SDSS). Radio morphology classes include core-only (core), core-lobe (lobe), core-jet (jet), lobe-core-lobe (triple), and double-lobe. Electronic tables of the quasar samples, along with spectral composites for individual morphology classes, are made available. We examine the optical colors of these subsamples and find that radio quasars with core emission unresolved by FIRST (on ∼5'' scale) have a redder color distribution than radio-quiet quasars (S 20 ∼ I ) are correlated, which supports the hypothesis that both parameters are indicative of line-of-sight orientation. We investigate spectral line equivalent widths (EWs) as a function of R and R I , including the O [III] narrow line doublet and the C IV λ1549 and Mg II λ2799 broad lines. We find that the rest EWs of the broad lines correlate positively with R I at the 4σ-8σ level. However, we find no strong dependence of EW on R, in contrast to previously published results. A possible interpretation of these results is that EWs of quasar emission lines increase as the line-of-sight angle to the radio-jet axis decreases. These results are in stark contrast to commonly accepted orientation-based theories, which suggest that continuum emission should increase as the angle to the radio-jet axis decreases, resulting in smaller EWs of emission lines (assumed isotropic). Finally, we observe the Baldwin effect in our sample and find that it does not depend strongly on quasar radio morphology.

  9. A Wealth of Dust Grains in Quasar Winds

    Science.gov (United States)

    2007-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version This plot of data captured by NASA's Spitzer Space Telescope reveals dust entrained in the winds rushing away from a quasar, or growing black hole. The quasar, called PG2112+059, is located deep inside a galaxy 8 billion light-years away. Astronomers believe the dust might have been forged in the winds, which would help explain where dust in the very early universe came from. The data were captured by Spitzer's infrared spectrograph, an instrument that splits apart light from the quasar into a spectrum that reveals telltale signs of different minerals. Each type of mineral, or dust grain, has a unique signature, as can be seen in the graph, or spectrum, above. The strongest features are from the mineral amorphous olivine, or glass (purple); the mineral forsterite found in sand (blue); and the mineral corundum found in rubies (light blue). The detection of forsterite and corundum is highly unusual in galaxies without quasars. Therefore, their presence is a key clue that these grains might have been created in the quasar winds and not by dying stars as they are in our Milky Way galaxy. Forsterite is destroyed quickly in normal galaxies by radiation, so it must be continually produced to be detected by Spitzer. Corundum is hard, and provides a seed that softer, more common minerals usually cover up. As a result, corundum is usually not seen in spectra of galaxies. Since Spitzer did detect the mineral, it is probably forming in a clumpy environment, which is expected in quasar winds. All together, the signatures of the unusual minerals in this spectrum point towards dust grains forming in the winds blowing away from quasars.

  10. Efficacy Trial of a Selective Prevention Program Targeting Both Eating Disorder Symptoms and Unhealthy Weight Gain among Female College Students

    Science.gov (United States)

    Stice, Eric; Rohde, Paul; Shaw, Heather; Marti, C. Nathan

    2012-01-01

    Objective: Evaluate a selective prevention program targeting both eating disorder symptoms and unhealthy weight gain in young women. Method: Female college students at high-risk for these outcomes by virtue of body image concerns (N = 398; M age = 18.4 years, SD = 0.6) were randomized to the Healthy Weight group-based 4-hr prevention program,…

  11. Optimal management of radial artery grafts in CABG: Patient and target vessel selection and anti-spasm therapy.

    Science.gov (United States)

    Schwann, Thomas A; Gaudino, Mario; Baldawi, Mustafa; Tranbaugh, Robert; Schwann, Alexandra N; Habib, Robert H

    2018-05-01

    The current literature on radial artery grafting is reviewed focusing on the optimal deployment of radial artery grafts in coronary artery bypass surgery with specific attention to the selection of patients and target vessels for radial artery grafting. © 2018 Wiley Periodicals, Inc.

  12. Trial-to-trial dynamics of selective long-term-memory retrieval with continuously changing retrieval targets.

    Science.gov (United States)

    Kizilirmak, Jasmin M; Rösler, Frank; Khader, Patrick H

    2014-10-01

    How do we control the successive retrieval of behaviorally relevant information from long-term memory (LTM) without being distracted by other potential retrieval targets associated to the same retrieval cues? Here, we approach this question by investigating the nature of trial-by-trial dynamics of selective LTM retrieval, i.e., in how far retrieval in one trial has detrimental or facilitatory effects on selective retrieval in the following trial. Participants first learned associations between retrieval cues and targets, with one cue always being linked to three targets, forming small associative networks. In successive trials, participants had to access either the same or a different target belonging to either the same or a different cue. We found that retrieval times were faster for targets that had already been relevant in the previous trial, with this facilitatory effect being substantially weaker when the associative network changed in which the targets were embedded. Moreover, staying within the same network still had a facilitatory effect even if the target changed, which became evident in a relatively higher memory performance in comparison to a network change. Furthermore, event-related brain potentials (ERPs) showed topographically and temporally dissociable correlates of these effects, suggesting that they result from combined influences of distinct processes that aid memory retrieval when relevant and irrelevant targets change their status from trial to trial. Taken together, the present study provides insight into the different processing stages of memory retrieval when fast switches between retrieval targets are required. Copyright © 2014 Elsevier Inc. All rights reserved.