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Arcodia R, Merloni A, Nandra K, Buchner J, Salvato M, Pasham D, Remillard R, Comparat J, Lamer G, Ponti G, Malyali A, Wolf J, Arzoumanian Z, Bogensberger D, Buckley DAH, Gendreau K, Gromadzki M, Kara E, Krumpe M, Markwardt C, Ramos-Ceja ME, Rau A, Schramm M, Schwope A. X-ray quasi-periodic eruptions from two previously quiescent galaxies. Nature 2021; 592:704-707. [PMID: 33911275 PMCID: PMC8081662 DOI: 10.1038/s41586-021-03394-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 02/25/2021] [Indexed: 11/22/2022]
Abstract
Quasi-periodic eruptions (QPEs) are very-high-amplitude bursts of X-ray radiation recurring every few hours and originating near the central supermassive black holes of galactic nuclei1,2. It is currently unknown what triggers these events, how long they last and how they are connected to the physical properties of the inner accretion flows. Previously, only two such sources were known, found either serendipitously or in archival data1,2, with emission lines in their optical spectra classifying their nuclei as hosting an actively accreting supermassive black hole3,4. Here we report observations of QPEs in two further galaxies, obtained with a blind and systematic search of half of the X-ray sky. The optical spectra of these galaxies show no signature of black hole activity, indicating that a pre-existing accretion flow that is typical of active galactic nuclei is not required to trigger these events. Indeed, the periods, amplitudes and profiles of the QPEs reported here are inconsistent with current models that invoke radiation-pressure-driven instabilities in the accretion disk5–9. Instead, QPEs might be driven by an orbiting compact object. Furthermore, their observed properties require the mass of the secondary object to be much smaller than that of the main body10, and future X-ray observations may constrain possible changes in their period owing to orbital evolution. This model could make QPEs a viable candidate for the electromagnetic counterparts of so-called extreme-mass-ratio inspirals11–13, with considerable implications for multi-messenger astrophysics and cosmology14,15. X-ray quasi-periodic eruptions are detected from two previously inactive galaxies, with observations suggesting that the very-high-amplitude X-ray bursts may arise from an orbiting compact object.
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Affiliation(s)
- R Arcodia
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany.
| | - A Merloni
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - K Nandra
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - J Buchner
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - M Salvato
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - D Pasham
- MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA, USA
| | - R Remillard
- MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA, USA
| | - J Comparat
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - G Lamer
- Leibniz-Institut für Astrophysik Potsdam (AIP), Potsdam, Germany
| | - G Ponti
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany.,INAF-Osservatorio Astronomico di Brera, Merate, Italy
| | - A Malyali
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - J Wolf
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - Z Arzoumanian
- Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - D Bogensberger
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - D A H Buckley
- South African Astronomical Observatory, Cape Town, South Africa
| | - K Gendreau
- Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - M Gromadzki
- Astronomical Observatory, University of Warsaw, Warsaw, Poland
| | - E Kara
- MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA, USA
| | - M Krumpe
- Leibniz-Institut für Astrophysik Potsdam (AIP), Potsdam, Germany
| | - C Markwardt
- Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - M E Ramos-Ceja
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - A Rau
- Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
| | - M Schramm
- Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - A Schwope
- Leibniz-Institut für Astrophysik Potsdam (AIP), Potsdam, Germany
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Mattila S, Pérez-Torres M, Efstathiou A, Mimica P, Fraser M, Kankare E, Alberdi A, Aloy MÁ, Heikkilä T, Jonker PG, Lundqvist P, Martí-Vidal I, Meikle WPS, Romero-Cañizales C, Smartt SJ, Tsygankov S, Varenius E, Alonso-Herrero A, Bondi M, Fransson C, Herrero-Illana R, Kangas T, Kotak R, Ramírez-Olivencia N, Väisänen P, Beswick RJ, Clements DL, Greimel R, Harmanen J, Kotilainen J, Nandra K, Reynolds T, Ryder S, Walton NA, Wiik K, Östlin G. A dust-enshrouded tidal disruption event with a resolved radio jet in a galaxy merger. Science 2018; 361:482-485. [PMID: 29903886 DOI: 10.1126/science.aao4669] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 06/01/2018] [Indexed: 11/02/2022]
Abstract
Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). We have observed a transient source in the western nucleus of the merging galaxy pair Arp 299 that radiated >1.5 × 1052 erg at infrared and radio wavelengths but was not luminous at optical or x-ray wavelengths. We interpret this as a TDE with much of its emission reradiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the difference between theoretical predictions and observed luminosities of TDEs. The radio observations resolve an expanding and decelerating jet, probing the jet formation and evolution around a SMBH.
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Affiliation(s)
- S Mattila
- Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland. .,Finnish Centre for Astronomy with ESO (FINCA), FI-20014 University of Turku, Finland
| | - M Pérez-Torres
- Instituto de Astrofísica de Andalucía-Consejo Superior de Investigaciones Científicas (CSIC), P.O. Box 3004, 18008, Granada, Spain. .,Departamento de Física Teórica, Facultad de Ciencias, Universidad de Zaragoza, 50019, Zaragoza, Spain
| | - A Efstathiou
- School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia, Cyprus
| | - P Mimica
- Departament d'Astronomia i Astrofisica, Universitat de València Estudi General, 46100 Burjassot, València, Spain
| | - M Fraser
- School of Physics, O'Brien Centre for Science North, University College Dublin, Belfield, Dublin 4, Ireland.,Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
| | - E Kankare
- Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK
| | - A Alberdi
- Instituto de Astrofísica de Andalucía-Consejo Superior de Investigaciones Científicas (CSIC), P.O. Box 3004, 18008, Granada, Spain
| | - M Á Aloy
- Departament d'Astronomia i Astrofisica, Universitat de València Estudi General, 46100 Burjassot, València, Spain
| | - T Heikkilä
- Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland
| | - P G Jonker
- SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, NL-3584 CA Utrecht, Netherlands.,Department of Astrophysics/Institute for Mathematics, Astrophysics and Particle Physics, Radboud University, P.O. Box 9010, 6500GL Nijmegen, Netherlands
| | - P Lundqvist
- Department of Astronomy and The Oskar Klein Centre, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm, Sweden
| | - I Martí-Vidal
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala, Sweden
| | - W P S Meikle
- Astrophysics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK
| | - C Romero-Cañizales
- Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China.,Núcleo de Astronomía de la Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, 8370191 Santiago, Chile
| | - S J Smartt
- Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK
| | - S Tsygankov
- Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland
| | - E Varenius
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala, Sweden.,Jodrell Bank Centre for Astrophysics, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - A Alonso-Herrero
- Centro de Astrobiología (CSIC-INTA), ESAC Campus, E-28692 Villanueva de la Cañada, Madrid, Spain
| | - M Bondi
- Istituto di Radioastronomia - Istituto Nazionale di Astrofisica (INAF), Bologna, via P. Gobetti 101, 40129, Bologna, Italy
| | - C Fransson
- Department of Astronomy and The Oskar Klein Centre, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm, Sweden
| | - R Herrero-Illana
- European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile
| | - T Kangas
- Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland.,Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
| | - R Kotak
- Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland.,Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK
| | - N Ramírez-Olivencia
- Instituto de Astrofísica de Andalucía-Consejo Superior de Investigaciones Científicas (CSIC), P.O. Box 3004, 18008, Granada, Spain
| | - P Väisänen
- South African Astronomical Observatory, P.O. Box 9, Observatory 7935, Cape Town, South Africa.,Southern African Large Telescope, P.O. Box 9, Observatory 7935, Cape Town, South Africa
| | - R J Beswick
- Jodrell Bank Centre for Astrophysics, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - D L Clements
- Astrophysics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK
| | - R Greimel
- Institute of Physics, Department for Geophysics, Astrophysics, and Meteorology, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - J Harmanen
- Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland
| | - J Kotilainen
- Finnish Centre for Astronomy with ESO (FINCA), FI-20014 University of Turku, Finland.,Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland
| | - K Nandra
- Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, 85748, Garching, Germany
| | - T Reynolds
- Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland
| | - S Ryder
- Australian Astronomical Observatory, 105 Delhi Rd, North Ryde, NSW 2113, Australia
| | - N A Walton
- Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
| | - K Wiik
- Tuorla Observatory, Department of Physics and Astronomy, FI-20014 University of Turku, Finland
| | - G Östlin
- Department of Astronomy and The Oskar Klein Centre, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm, Sweden
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Götz D, Osborne J, Cordier B, Paul J, Evans P, Beardmore A, Martindale A, Willingale R, O'Brien P, Basa S, Rossin C, Godet O, Webb N, Greiner J, Nandra K, Meidinger N, Perinati E, Santangelo A, Mercier K, Gonzalez F. The microchannel x-ray telescope for the gamma-ray burst mission SVOM. ACTA ACUST UNITED AC 2014. [DOI: 10.1117/12.2054898] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Kaastra JS, Kriss GA, Cappi M, Mehdipour M, Petrucci PO, Steenbrugge KC, Arav N, Behar E, Bianchi S, Boissay R, Branduardi-Raymont G, Chamberlain C, Costantini E, Ely JC, Ebrero J, Di Gesu L, Harrison FA, Kaspi S, Malzac J, De Marco B, Matt G, Nandra K, Paltani S, Person R, Peterson BM, Pinto C, Ponti G, Pozo Nuñez F, De Rosa A, Seta H, Ursini F, de Vries CP, Walton DJ, Whewell M. Active galaxies. A fast and long-lived outflow from the supermassive black hole in NGC 5548. Science 2014; 345:64-8. [PMID: 24994647 DOI: 10.1126/science.1253787] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution x-ray and ultraviolet (UV) observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six space observatories shows the nucleus to be obscured by a long-lasting, clumpy stream of ionized gas not seen before. It blocks 90% of the soft x-ray emission and causes simultaneous deep, broad UV absorption troughs. The outflow velocities of this gas are up to five times faster than those in the persistent outflow, and, at a distance of only a few light days from the nucleus, it may likely originate from the accretion disk.
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Affiliation(s)
- J S Kaastra
- SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands. Department of Physics and Astronomy, Universiteit Utrecht, Post Office Box 80000, 3508 TA Utrecht, Netherlands. Leiden Observatory, Leiden University, Post Office Box 9513, 2300 RA Leiden, Netherlands.
| | - G A Kriss
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
| | - M Cappi
- Istituto Nazionale di Astrofisica (INAF)-Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF) Bologna, Via Gobetti 101, I-40129 Bologna, Italy
| | - M Mehdipour
- SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands. Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
| | - P-O Petrucci
- Université Grenoble Alpes, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), F-38000 Grenoble, France. CNRS, IPAG, F-38000 Grenoble, France
| | - K C Steenbrugge
- Instituto de Astronomía, Universidad Católica del Norte, Avenida Angamos 0610, Casilla 1280, Antofagasta, Chile. Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
| | - N Arav
- Department of Physics, Virginia Tech, Blacksburg, VA 24061, USA
| | - E Behar
- Department of Physics, Technion-Israel Institute of Technology, 32000 Haifa, Israel
| | - S Bianchi
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
| | - R Boissay
- Department of Astronomy, University of Geneva, 16 Chemin d'Ecogia, 1290 Versoix, Switzerland
| | - G Branduardi-Raymont
- Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
| | - C Chamberlain
- Department of Physics, Virginia Tech, Blacksburg, VA 24061, USA
| | - E Costantini
- SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands
| | - J C Ely
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
| | - J Ebrero
- SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands. European Space Astronomy Centre, Post Office Box 78, E-28691 Villanueva de la Cañada, Madrid, Spain
| | - L Di Gesu
- SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands
| | - F A Harrison
- Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
| | - S Kaspi
- Department of Physics, Technion-Israel Institute of Technology, 32000 Haifa, Israel
| | - J Malzac
- Université de Toulouse, Université Paul Sabatier (UPS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche en Astrophysique et Planélogie (IRAP), Toulouse, France. CNRS, IRAP, 9 Avenue colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
| | - B De Marco
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany
| | - G Matt
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
| | - K Nandra
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany
| | - S Paltani
- Department of Astronomy, University of Geneva, 16 Chemin d'Ecogia, 1290 Versoix, Switzerland
| | - R Person
- 22 Impasse du Bois Joli, 74410 St. Jorioz, France
| | - B M Peterson
- Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA. Center for Cosmology and AstroParticle Physics, Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA
| | - C Pinto
- Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
| | - G Ponti
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany
| | - F Pozo Nuñez
- Astronomisches Institut, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany
| | - A De Rosa
- INAF/Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, I-00133 Roma, Italy
| | - H Seta
- Research Center for Measurement in Advanced Science, Faculty of Science, Rikkyo University 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, Japan. Department of Physics, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan
| | - F Ursini
- Université Grenoble Alpes, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), F-38000 Grenoble, France. CNRS, IPAG, F-38000 Grenoble, France
| | - C P de Vries
- SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands
| | - D J Walton
- Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
| | - M Whewell
- Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
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Hicks RM, Turton JA, Chowaniec J, Tomlinson CN, Gwynne J, Nandra K, Chrysostomou E, Pedrick M. Modulation of carcinogenesis in the urinary bladder by retinoids. Ciba Found Symp 2008; 113:168-90. [PMID: 3849405 DOI: 10.1002/9780470720943.ch11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Bladder cancer has a 70% recurrence rate within five years and a high associated mortality. It commonly occurs in one or both of two predominant growth/behaviour patterns: either well-differentiated, relatively benign exophytic papillary lesions, or flat, poorly differentiated invasive carcinoma usually arising from carcinoma-in-situ. We have used the F344 rat treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) as a model for the papillary disease, and the BBN-treated B6D2F1 mouse for flat, invasive bladder carcinoma. In the rat, carcinogenesis is a multistage process and several retinoids will delay or even halt the development of bladder cancer. Inhibition of carcinogenesis is not complete, but there is a consistent reduction in the time-related incidence of papillomas and carcinomas and a concomitant improvement in the overall differentiation of the urothelium. In the BBN/mouse model, retinoids also have anticarcinogenic activity but interpretation of the results is more complicated. Unlike the F344 rat, the B6D2F1 mouse has a non-uniform response to BBN; not all mice develop bladder cancer even after treatment with very high doses of BBN and in those that do, more than one mechanism of carcinogenesis may be involved. Individual retinoids differ markedly in their ability to modulate bladder carcinogenesis in rodents; the behaviour of one analogue cannot be predicted automatically from data obtained with another. Combined data from rodent trials in this and other laboratories have identified N-(4-hydroxyphenyl)retinamide (HPR) as the most anticarcinogenic retinoid tested so far for the rodent bladder. It is also less toxic in rodents and better tolerated in humans than either 13-cis-retinoic acid or etretinate, two retinoids currently used in dermatological practice. A prophylactic chemopreventive trial of HPR in bladder cancer patients starting in 1985 will be centered on the Middlesex Hospital, London.
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García SC, Pedernera M, Fulkerson WJ, Horadagoda A, Nandra K. Feeding concentrates based on individual cow requirements improves the yield of milk solids in dairy cows grazing restricted pasture. ACTA ACUST UNITED AC 2007. [DOI: 10.1071/ea05349] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A grazing experiment involving 50 lactating Holstein–Friesian dairy cows was conducted to test the hypothesis that feeding concentrates (range 3–7 kg as fed/cow.day; average 5 kg/cow.day) to grazing cows based on individual (I) cow requirements would increase milk solids yield in comparison to fixed rate (F) allocation to the whole herd (average 5 kg/cow.day for all cows). The experiment comprised two sequential periods that differed only in the way maize silage was offered to cows (either 100% on a feed pad at night or 75% on a feed pad at night, with 25% in a paddock in the morning). Intake of individual cows was estimated using the 13C and n-alkanes method. The rumen degradability of the feeds (lucerne pasture, maize silage and commercial dairy pellets) was measured in parallel, using six rumen-fistulated sheep. Compared with cows in the F group, milk yield and milk fat yield for the I cows increased (P < 0.05) by 3.0 and 11.1%, respectively. As neither milk protein content nor milk protein yield was affected (P > 0.05) by treatment, total milk solids yield (milk fat plus milk protein) was 7.0% higher (P < 0.05) for I cows than for F cows. The increase in milk fat yield was presumably associated with an improved diet nutrient balance in the I cows, as indicated by a significant correlation between fibre intake and milk fat yield for cows in the I group but not for cows in the F group. This is also supported by the results of the rumen degradability of the feeds. In this study, higher-producing cows compensated for their higher requirements by increasing intake of maize silage, rather than pasture, as the former was the less restricted feed on offer. This highlights the importance of offering at least one feed to cows in a less restricted way, in order to enable high-producing cows in the herd to compensate for their higher intake requirements. In conclusion, under the conditions of the present study, feeding concentrates to cows based on individual cow requirements increased milk solids yield at no extra cost.
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Yaqoob T, George IM, Nandra K, Turner TJ, Zobair S, Serlemitsos PJ. A Highly Doppler Blueshifted Fe-K Emission Line in the High-Redshift QSO PKS 2149-306. Astrophys J 1999; 525:L9-L12. [PMID: 10511501 DOI: 10.1086/312327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We report the results from an ASCA observation of the high-luminosity, radio-loud quasar PKS 2149-306 (redshift 2.345), covering the approximately 1.7-30 keV band in the quasar frame. We find the source to have a luminosity approximately 6x1047 ergs s-1 in the 2-10 keV band (quasar frame). We detect an emission line centered at approximately 17 keV in the quasar frame. Line emission at this energy has not been observed in any other active galaxy or quasar to date. We present evidence rejecting the possibility that this line is the result of instrumental artifacts or a serendipitous source. The most likely explanation is blueshifted Fe-K emission (the equivalent width is EW approximately 300+/-200 eV, quasar frame). Bulk velocities of the order of 0.75c are implied by the data. We show that Fe-K line photons originating in an accretion disk and Compton scattering off a leptonic jet aligned along the disk axis can account for the emission line. Curiously, if the emission-line feature recently discovered in another quasar (PKS 0637-752, z=0.654) at 1.6 keV in the quasar frame is due to blueshifted O vii emission, the Doppler blueshifting factor in both quasars is similar ( approximately 2.7-2.8).
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Abstract
Ciliogenesis of the respiratory epithelium in the human cartilaginous trachea start during the 12th week of gestation. Ciliary shafts are first seen under the scanning electron microscope during the 13th week. Unlike its membranous counterpart, ciliary shafts appear all over the epithelial surface at almost the same time. Epithelial cells destined to become ciliated cells first develop numerous long and thin microvilli. A process of individual cell extrusion and proliferation of neuroepithelial bodies around the carinal angle precede ciliation in the respiratory epithelium of the cartilaginous trachea. Epithelial cell differentiation patterns in both the cartilaginous and membranous trachea are different. The mechanisms involved in modulating cell differentiation are currently under investigation.
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Affiliation(s)
- G Moscoso
- Department of Morbid Anatomy, King's College Hospital, London, England
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