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  • 1
    Publication Date: 2013-10-18
    Description: Super-luminous supernovae that radiate more than 10(44) ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of (56)Ni are synthesized; this isotope decays to (56)Fe via (56)Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 x 10(-6) times that of the core-collapse rate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nicholl, M -- Smartt, S J -- Jerkstrand, A -- Inserra, C -- McCrum, M -- Kotak, R -- Fraser, M -- Wright, D -- Chen, T-W -- Smith, K -- Young, D R -- Sim, S A -- Valenti, S -- Howell, D A -- Bresolin, F -- Kudritzki, R P -- Tonry, J L -- Huber, M E -- Rest, A -- Pastorello, A -- Tomasella, L -- Cappellaro, E -- Benetti, S -- Mattila, S -- Kankare, E -- Kangas, T -- Leloudas, G -- Sollerman, J -- Taddia, F -- Berger, E -- Chornock, R -- Narayan, G -- Stubbs, C W -- Foley, R J -- Lunnan, R -- Soderberg, A -- Sanders, N -- Milisavljevic, D -- Margutti, R -- Kirshner, R P -- Elias-Rosa, N -- Morales-Garoffolo, A -- Taubenberger, S -- Botticella, M T -- Gezari, S -- Urata, Y -- Rodney, S -- Riess, A G -- Scolnic, D -- Wood-Vasey, W M -- Burgett, W S -- Chambers, K -- Flewelling, H A -- Magnier, E A -- Kaiser, N -- Metcalfe, N -- Morgan, J -- Price, P A -- Sweeney, W -- Waters, C -- England -- Nature. 2013 Oct 17;502(7471):346-9. doi: 10.1038/nature12569.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK. mnicholl03@qub.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24132291" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    ISSN: 1432-0827
    Keywords: Immobilization ; Metabolic alkalosis ; Renal acid excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We studied the systemic and renal acid—base response of monkeys during ten weeks of immobilization. By three weeks of immobilization, arterial pH and bicarbonate concentrations were elevated (chronic metabolic alkalosis). Net urinary acid excretion increased in immobilized animals. Urinary bicarbonate excretion decreased during the first three weeks of immobilization, and then returned to control levels. Sustained increases in urinary ammonium excretion were seen throughout the time duration of immobilization. Neither potassium depletion nor hypokalemia was observed. Most parameters returned promptly to the normal range during the first week of recovery. Factors tentatively associated with changes in acid—base status of monkeys include contraction of extracellular fluid volume, retention of bicarbonate, increased acid excretion, and possible participation of extrarenal buffers.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0827
    Keywords: Bone ; Osteopenia ; Noninvasive monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Radiological techniques were utilized for monitoring progressive changes in compact bone in the tibia of monkeys during experimentally induced osteopenia. Bone mass loss in the tibia during restraint was evaluated from radiographs, from bone mineral analysis, and from images reconstructed from gamma ray computerized tomography. The losses during 6 months of restraint tended to occur predominantly in the proximal tibia and were characterized by subperiosteal bone loss, intracortical striations, and scalloped endosteal surfaces. Bone mineral content in the cross section of the tibia declined 17–21%. Tomography demonstrated endosteal widening and reduced mineral content per unit of thickness of cortical bone. In 6 months of recovery, the mineral content of the proximal tibia remained depressed. Effects of the dynamic environment on local-regional changes in various skeletal areas are discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0827
    Keywords: Bone ; Bending rigidity ; Disuse atrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The in vivo bending rigidity and bone mineral content of monkey ulnae and tibiae were measured. Bending rigidity in the anteroposterior plane was measured by an impedance probe technique. Forced vibrations of the bones were induced with an electromechanical shaker, and force and velocity at the driving point were determined. The responses over the range of 100–250 Hz were utilized to compute the bending rigidity. Bone mineral content in the cross section was determined by a photon absorption technique. Seventeen male monkeys (Macaca nemestrina) weighing 6–14 kg were evaluated. Repeatability of the rigidity measures was 4%. Bone mineral content was measured with a precision of 3.5%. Bending rigidity was correlated with the mineral content of the cross section,r=0.899. Two monkeys were evaluated during prolonged hypodynamic restraint. Restraint produced regional losses of bone most obviously in the proximal tibia. Local bone mineral content declines 17 to 24% and the average bending rigidity declines 12 to 22%. Changes in bones leading to a reduction in mineral content and stiffness are discussed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0827
    Keywords: Immobilization ; Bone strength ; Resorption ; Recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We studied the mechanical properties and structural changes in the monkey tibia with disuse osteoporosis and during subsequent recovery. Bone bending stiffness was evaluated in relationship to microscopic changes in cortical bone and Norland bone mineral analysis. Restraint in the semireclined position produced regional losses of bone most obviously in the anterior-proximal tibiae. Following 6 months of restraint, the greatest losses of bone mineral in the proximal tibiae ranged from 23% to 31%; the largest changes in bone stiffness ranged from 36% to 40%. Approximately 8 ½ months of recovery were required for restoration of normal bending properties. However, even after 15 months of recovery, bone mineral content did not necessarily return to normal levels. Histologically, resorption cavities in cortical bone were seen within 1 month of restraint; by 2 ½ months of restraint there were large resorption cavities subperiosteally, endosteally, and intracortically. After 15 months of recovery, the cortex consisted mainly of first-generation haversian systems. After 40 months, the cortex appeared normal with numerous secondary and tertiary generations of haversian systems.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 206 (1965), S. 803-806 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] MARINE organisms collected along the California Coast in 1963 and examined1 for 54Mn and 65Zn by ordinary ?-spectrometry often appeared to contain in addition small traces of 60Co. As cobalt is believed to be essential to normal growth for many -organisms and 60Co is a radio-label which decays ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 200 (1963), S. 327-329 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] IT has been estimated1 that 855 curies of zinc-65 enter the Pacific each day at the mouth of the Columbia River along with other nuclides arising from activation of cooling water constituents at Hanford. Osterberg2'3 and others1 have reported extensively on concentrations of zinc-65 in marine ...
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 234 (1971), S. 347-347 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] First, we did not mean to imply that the 108mAg and 110mAg observed in the Pacific marine organisms was actually produced primarily by thermal neutron activation of stable silver; only that the assumption of an initial 110mAg/108mAg activity ratio value of 162 yielded apparently reasonable dates of ...
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 227 (1970), S. 941-943 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The short-lived (253 days) 110mAg was determined in 1964 (ref. 2); on the other hand, a recently installed two-dimensional y-ray spectrometer of a type developed by the Hanford group3 was used for measuring 108mAg. Table 1 lists the activities of 108mAg found in samples of squid, mussel, lobster, ...
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2291-2298 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report depth profiles of the hydrogen concentrations in metal-oxide-semiconductor structures measured using the nuclear reaction profiling technique with a 6.4-MeV 15N beam. In both conventionally grown and ultra-dry thermal oxide samples with aluminum or gold gate metal, a peak of hydrogen concentration is observed at the metal/SiO2 interface. The amount of hydrogen at this interface varied from sample to sample in the range 2–6×1015 H/cm2, which was at least 20 times as much as in the SiO2 layers. By continued irradiation with the measuring beam, most of this hydrogen was detrapped from the metal/SiO2 interface and diffused into the SiO2. The detrapping occurred much more rapidly in samples made with Al metallization than in Au gate or unmetallized samples. The data can be fitted by a model in which hydrogen is detrapped from the metal/SiO2 interface by the beam, then diffuses into the SiO2. Redistribution of hydrogen was found to continue until it was uniformly distributed throughout the SiO2, with a residual peak of strongly trapped hydrogen remaining at the metal/SiO2 boundary. At the same time the concentration of hydrogen in the SiO2 increased from an initial low level to about 4×1020 cm−3, depending on the amount of hydrogen initially at the Al/SiO2 interface.
    Type of Medium: Electronic Resource
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